MTN upgrade problems

I upgraded my contract 3 weeks ago - 7 June 2024. From the moment it was upgraded I have not had an incoming call from any numbers other than MTN numbers. I have reported it, spent 3 hours at an MTN shop, yet, no joy. I receive business call on this number and this is very very bad for my business, YET, come invoice time I have to take the full knock, regardless. Sorry does not help anymore and no reply will force me to report itnto the Ombudsman.