Phone number testing is the process of verifying that inbound telephone numbers connect correctly, route to the intended destination, and deliver acceptable voice quality.
International toll and toll-free phone number testing is crucial to protect one of your key customer contact channels. Businesses today rely on multiple contact channels to give customers options, and to provide a level of self-service.
Phone number testing ensures your inbound numbers connect reliably, route correctly, and maintain high voice quality. Key methods include automated connection verification, PESQ voice quality scoring, and DTMF/CLI monitoring. Testing safeguards revenue, customer satisfaction, and brand reputation.
Why should you consider phone number testing?
According to Call Center Helper, telephone contact remains the dominant channel, responsible for 63.6% of interactions.
The modern customer expects that the telephone number they dialed will work. Hence, it should work the first time and every time they call. Additionally, the call quality should be first class. Whatever the business transaction may be, it should be quick and effective.
Testing safeguards revenue, customer satisfaction, and brand reputation, making it essential for any business relying on inbound phone services.
What are global inbound services?
Global inbound services are telecommunications solutions that enable customers worldwide to reach a business’s contact center through various access numbers.
Types of global inbound services include:
- Toll-free numbers — Free for callers, costs absorbed by the business
- Local access numbers — Dialable from anywhere, appear local to customers
- Universal International Freephone Numbers (UIFN) — Single number accessible across multiple countries
- Premium-rate numbers — Callers pay a premium, often for specialized services
- Shared-cost numbers — Costs split between caller and business
Services use traditional time-division multiplexing (TDM) technology, via private internet protocol (IP) or via voice over IP (VoIP).
Contact centers can take advantage of the concept of a call-forward to deliver callers to strategic sites. At these sites, the appropriate language skills and product expertise are at hand to give customers the help they need, when they need it.
By centralizing services in this way, businesses are able to ensure service consistency while getting economies of scale. Customers are able to dial a number that is local and accessible to them and are offered support in their native language.
Being global, these services rely on multiple telecommunications networks. Calls often originate in one country and terminate in another. Even the biggest telecoms providers will frequently use partnerships with other network operators to offer broader geographical coverage. Additionally, calls may originate on a cellular network and terminate on an IP or TDM network. Regulatory jurisdictions and technologies often mix with differing styles of network management, so occasionally, problems can and do arise.
International call routing is complex. Therefore, phone number testing is a necessity. Businesses rely on these critical services to generate revenue and to maintain high levels of customer satisfaction.
How to test phone numbers
Core steps for phone number testing:
- Verify connection — Confirm the number connects and answers.
- Validate routing — Validate that calls land at the correct destination.
- Measure voice quality — Assess audio clarity using PESQ or MOS scoring.
- Test call attributes — Verify DTMF tones and CLI/Caller ID pass correctly.
- Automate and scale — Use automated testing tools for consistent, repeatable results.
The type of number in question has a direct impact on how simple the process of testing the phone number will be. While local access numbers are dialable from anywhere; toll-free numbers often carry restrictions and are only dialable from within the country. While a local access number is dialable from anywhere, dialing this number from everywhere may not be a reasonable requirement for the testing team.
For example, a Paris, France local access number might point to a contact center in Malaysia. If someone dials that Paris number from New York, intelligent network routing will identify the target destination and deliver the call without transiting through any French network. Any problem situation that impacts users in the local French networks then becomes masked. A true test design uses the service exactly as a customer would; from within that particular country.
What’s more, while dialing a single number manually might be a simple task, it does not scale well. Contact center infrastructures may have extensive dial-plans with many, many phone numbers. Manually testing all of these numbers can often be resource consuming, expensive, and produce inconsistent results. Automated methods used to test phone numbers provide more real and accurate network insights and quality assurance.
Testing phone number connection
A successful connection test confirms that a dialed number rings, answers, and routes to the correct destination without encountering busy signals or misrouting.
Your first priority is to determine if your number is connecting.
Dialing a number should always result in a ring-tone and crucially an answer! Global inbound services are generally set up so that multiple simultaneous callers can use the number. Users should not encounter an engaged tone.
Critically, when the number connects, you will want to be sure it connects to your contact center and that it lands correctly. Unfortunately, many contact center managers will have experienced moments where their key inbound numbers were accidentally redirected to another business or even a private residence. Thankfully, automated verification is now possible.
Phone number quality testing
Once you know that your numbers are connecting, you will want to verify that the voice quality is there to support positive customer interaction.
Historically, mean opinion scoring (MOS) was used to judge telephone quality. In MOS testing, human participants would rate a phone call based on their experience of it. However, the resulting quality indication was naturally subjective.
MOS methodology has since evolved to support automated testing, however more sophisticated options have now overtaken it. Perceptual Evaluation of Speech Quality (PESQ) is an ITU standard (ITU-T P.862) that objectively measures audio quality by comparing a reference audio signal to the degraded signal received after transmission. PESQ takes into consideration characteristics such as:
- Audio sharpness
- Call volume
- Background noise
- Variable latency or lag in audio
- Clipping
- Audio interference
With PESQ, the voice quality on phone calls, including mobile or fixed-lines, toll and toll-free services, VoIP or public switched telephone network (PSTN), can be assessed to an agreed international standard. With this, there’s no ambiguity, so you know exactly how your phone services are performing.
Voice quality reporting uses a numerical scale and benchmarking which makes it possible to measure against historical performance or against other services. Efforts to improve quality can be assessed easily and objectively.
Key metrics for phone number quality testing
- Perceptual Evaluation of Speech Quality (PESQ) — ITU-T P.862 standard for objective voice quality measurement; a score above 3.5 indicates good quality.
- Mean opinion score (MOS) — Scale of 1-5 rating perceived call quality; scores above 4.0 are considered excellent.
- Connection success rate — Percentage of calls that connect successfully; should exceed 99% for reliable service.
- DTMF verification — Confirms touch-tone signals transmit correctly for IVR. navigation
- CLI/Caller ID validation — Verifies calling line identification passes end-to-end.
Monitoring key call attributes
Several other call attributes are also important to the contact center.
DTMF or touch-tone is often fundamental to interactive voice response (IVR) navigation. This allows users to quickly find the service they require through keypad menu selection.
Caller ID or calling line identification (CLI) is often used to identify the caller or the geographic location from which a call originated. As a result, contact center software has some fantastic functions that leverage CLI presentation to improve business performance for inbound and outbound calls.
While a call connection might be successful, call attributes such as these may present problems. Occasionally, when transiting international interconnects, etc. call aspects may not be maintained end-to-end. Careful monitoring ensures services can better support a contact center’s key business processes.
Reap the benefits of phone number testing
Make sure your key customer communication channel is supporting great customer conversations. For more information see our Cyara Voice Assure product page or contact our team to arrange a demo and see how you could benefit from automated phone number testing.
Frequently Asked Questions
Phone number testing is the process of verifying that inbound telephone numbers connect correctly, route to the intended destination, and deliver acceptable voice quality for customer interactions.
Critical inbound numbers should be tested continuously or at regular intervals (daily or weekly minimum) to catch issues before they impact customers. High-volume or revenue-generating numbers may require real-time monitoring.
Mean opinion score (MOS) was originally based on subjective human ratings of call quality, while Perceptual Evaluation of Speech Quality (PESQ) is an automated, objective measurement standard (ITU-T P.862) that algorithmically assesses voice quality.
Toll-free numbers are often restricted to callers within a specific country. Testing from within that country ensures the call traverses the same network paths that actual customers use, revealing issues that international test calls might miss.
Common causes include carrier configuration errors, number porting issues, network outages, incorrect call-forwarding settings, and problems at international interconnect points.
Telephone contact accounts for 63.6% of customer interactions, making it a critical channel for businesses. Testing ensures your numbers connect reliably and deliver the call quality customers expect every time they call.
Toll-free numbers are often only dialable from within their country, and testing from outside can mask local network issues. A true test replicates the experience of a local customer, including the specific routing and infrastructure they encounter.
Manually dialing numbers does not scale well across large dial-plans and produces inconsistent results. Automated testing provides more accurate network insights and quality assurance across many numbers simultaneously.
Cyara uses PESQ, an ITU standard that objectively measures audio sharpness, call volume, background noise, latency, clipping, and audio interference. This replaces the older, subjective mean opinion scoring approach.
DTMF (touch-tone) functionality and caller ID (CLI) presentation are both important to monitor. These attributes can degrade when calls transit international interconnects, which can disrupt IVR navigation and contact center workflows that rely on caller identification.
Global inbound services give customers access to contact centers through toll-free, local, and universal freephone numbers across multiple telecommunications networks. Because calls often originate in one country and terminate in another across different network types, routing complexity makes regular testing a necessity.
Yes, automated verification can confirm that a number not only connects but routes correctly to the intended contact center. This helps catch situations where inbound numbers are accidentally redirected to the wrong destination.
