This page has been created to help callers report an on going call issue.

What we have gathered so far;

Calls made to the range of numbers 028 8781 7010 to 028 8781 7027 are succeeding to get through about 50% of the time.

If you use a mobile phone to call the numbers within this range and the call fails, you should be presented with the reason the call failed. The error on some phones is 'Number not valid' or 'Invalid number' depending n the type of phone you are using.

However, if you continue to retry ringing the number, you should get through within a few tries.

So far, this error only appears to occur with a single carrier which we are unable to name, for obvious reasons. The carrier in question has admitted there is a 'network issue' but is taking much longer than we feel they should to resolve it.

Issue specifications

The caller may be anywhere in the UK where the carrier is present so the issue is NOT location specific.

The issue is present whether the caller has a strong or weak mobile phone signal. This may be verified by calling known working numbers from your location.

The error occurs no matter what make or model of phone the caller uses.

The error occurs whether or not the caller has a new or older SIM card.

You may be told that you are ringing from an area where the service is being upgraded from 4g to 5g. The issue is intermittent and is not location specific so this can be ruled out.

Contact your carrier

If your call fails to one of the numbers above, please contact your carrier and report it.

The more people who report it, the better the chance of the carrier resolving it. Use the information above in the 'Issue specifications' to describe the issue to your carrier and insist, if you can, that they look into it as soon as possible and report back to you when it has been resolved.

Contact us regarding the issue

If you would like to help us to help the carrier to resolve this issue, please email any constructive information to roger.craig@028ni.com including as much of the following information as possible.

1 - The time and date you called one of the numbers within the range.

2 - The carrier you are using (for example BT, Sky, Three, Vodafone, EE etc..).

3 - The number of times you got through and the number of times you did not get through.

4 - Your location - nearest town / post code / county will do.

5 - The error which comes up on your phone (normally 'Number not valid' or 'Invalid number').

This information will then be passed on to the relevant carrier to help them isolate and resolve the issue.

5/1/22 Amendment.
Call diversion on numbers within the range. If the call gets through to our platform, it will divert normally. If not, the person calling will get a 'Number not valid' or 'Invalid number' error.

All the number within the range from 02887817000 to 02887817999 exhibit this problem - from only one carrier (and its associates). This issue is present irrespective of the recipients carrier.

10/1/23 Faulting carrier called, requesting range of failing numbers and to investigate further.

20/1/23 Escalated to networks team with 72 hours to respond.

24/1/23 Twenty calls made to two different numbers within the range and all worked. Official confirmation of resolution pending.


This web page has been created specifically for dealing with an ongoing issue with a carrier which cannot reliably connect to a selection of numbers as outlined above. Once the issue has been resolved, this website will be taken down. We are grateful for any help you may provide. Your help will be private and confidential and will only be used for the resolution of the issue in question, however we may contact you for further clarification if we feel it will be beneficial. The issue is extremely unusual and difficult to pin down so every bit of help is greatly appreciated

Although the issue appears to be with a single carrier, other phone company's use the carrier in question so it may appear that other carriers are at fault. This is why it is important so send us as much relevant, accurate information as possible. This page will be updated with any relevant information as it becomes available.