5 reasons why phone numbers can and do fail, and how to avoid it

You might have the slickest omnichannel campaigning, a website that ranks #1 on Google, and the best product on the market, but if your phone number doesn’t work, none of it matters. 

Dead phone numbers are a debilitatingly expensive problem. A report by The Software Bureau estimates that inaccurate data, including incorrect contact details like email addresses and phone numbers, costs the UK’s economy £900 billion every year. The problem with phone number faults is that they don’t always fail loudly and are easy to miss. You won’t get an alert. You’ll simply stop receiving calls, and unless you’re receiving hundreds of calls a day, a fault can sit quietly in the background for weeks before anyone realises. By then, the damage is done.  

In this guide, Gtele.com unpacks the hidden cost of a dead number. We explore the 5 most common reasons why international numbers fail, and what you can do to protect your customer experience with live phone number testing. 

The hidden cost of a dead number 

When a phone number fails, the impact is rarely just one missed call. It’s… 

…lost leads from customers ready to buy. 

…broken customer journeys, where they tried calling but couldn’t get through. 

…wasted marketing spend on branding, paid traffic, and directories. 

…poor CX that lingers long after the issue is fixed. 

…reputational damage, because if you can’t answer calls, can you deliver on your promise? 

That’s why proactive phone number testing isn’t a nice-to-have – it’s a simple form of insurance for your inbound performance. 

The 5 most common reasons phone numbers fail 

International numbering adds more variables: more carriers, more routing layers, more compliance rules, and more points of failure. Gtele.com’s live phone number testing page sums it up perfectly – faults happen, and there’s a long list of reasons numbers may not work.  

Here are the 5 most common culprits, with real-world examples of their impact, and a recommended fix for each: 

Reason 1: Carriers switch numbers off for low or no usage 

Some businesses’ phone numbers may receive sporadic or seasonal traffic – and that’s where trouble starts. Certain carriers deactivate or suspend lines with low usage, especially if they’re seen as dormant.  

This is common with: 

• Emergency / disaster lines 

• Rarely used support lines 

• Numbers printed on product packaging or brochures 

Fix: Scheduled testing not only keeps numbers ‘alive’, it also flags issues early, and well before a customer does!  

Reason 2: Regulations and compliance requirements change 

International numbering is heavily regulated. If in-country rules change and your business is no longer compliant, the carrier may be forced to switch the number off.  

Fix: Keep your compliance / KYC documentation current, and add testing into your ongoing governance – especially if you have numbers across multiple countries. Visit our Compliance Hub to learn more. 

Reason 3: Call forwarding wasn’t updated after a business change 

Moves, migrations, office closures, call centre changes, new CRMs – these are the everyday realities of growing businesses. Unfortunately, they’re also a top reason numbers fail.  

Fix: Whenever your business changes, make a routing review part of the checklist that takes into account your business needs, such as your staff comms, and whether you require an IVR or contact centre solution for external callers. 

Reason 4: Network faults  

Sometimes, the issue isn’t configuration – it’s a genuine network fault that could either lie with the customer’s local network provider, or the destination where calls are routed. 

Fix: Live, in-country phone number testing helps isolate where the problem sits, so you can escalate to the right provider quickly. 

Reason 5: Old IVRs and legacy call flows 

IVRs age badly. Teams change. Departments move. Some options become irrelevant. Gtele.com highlights a classic scenario: an IVR created years ago may still forward to a section of your business that’s since closed down or relocated.  

Fix: Test your full customer journey. Don’t just ask, “does it ring?”, but include IVR option paths, queue behaviour, and out-of-hours routing. 

What a good test report should include 

Testing is only valuable if the reporting is clear, traceable, and actionable. 

Gtele.com’s post-test report includes:  

• Time and date the test call was made 

• Country of origin and in-country number used  

• Number dialled 

• Call result that shows whether the call connected / failed / busy / no answer, etc. 

• Call recording so you can listen back 

Recordings are key because they let you verify the experience end-to-end – audio quality, announcements, IVR prompts, agent greeting, and any unexpected routing outcomes.  

One-off vs scheduled testing: which do you need? 

There’s no one-size-fits-all solution to phone number testing, because this need depends on how critical the number is and how widely it’s published. Let’s look at what approach might work for you: 

One-off testing  

Ideal for: 

• Launches and organised events 

• New numbers before they go live in ads or on your website 

• Numbers you’ve inherited from a previous provider 

• Spot-checking after routing changes 

Scheduled testing  

Use this when: 

• You have a mission-critical number 

• The number is printed on packaging, literature, or signage 

• You operate across many countries 

• The number supports urgent customer needs 

• Your call flows change often 

Gtele.com offers simple in-country tests from just £20:  

We can schedule phone number testing at intervals you choose, with reliable scheduling for ongoing assurance.  

Quick self-audit checklist  

If you manage global numbers, this checklist can help prevent any nasty surprises: 

• IVR paths 

Do all menu options still go somewhere useful?  

• Forwarding destinations 

Are calls routing to the correct site/call centre/team?  

• Out-of-hours + busy handling 

Where do calls go when lines are busy or closed? 

• Compliance / KYC 

Are your local documents current?  

• Test from landline and mobile 

Customers don’t all call the same way – your testing shouldn’t either.  

Protect your inbound experience before it breaks 

The brands that win globally aren’t just the ones with international reach – they’re the ones with reliability. Live testing keeps your numbers healthy, protects your customer experience, and ensures every inbound opportunity actually connects. 

Send us your list of numbers to test. Go to our live phone number testing page to start.