MTN - cant resolve a incoming call issue on a contract

Around 12 – 18 months ago I started getting complaints that when people call , my cell would ring 3 times and say “ the number you have dialled doesn’t exist “

I called the call centre and requested that they look into the issue and activate the VM on my line They told me it was active but has not worked since this issue started.

The call centre tried to reset my sim multiple times and I followed the instructions to no avail.

I then did a sim swap at the MTN store hoping this would work – the problem persisted however now instead of 3 rings it has the normal amount of rings and when it would switch to VM it gives the voice prompt “ the number you have dialled doesn’t exist “

Since the sim swap ive spoken to the call centre and have done the sim reset again , nothing changed.

I tried my sim in another handset and the problem persists Number is ***