MTN sim swap

I took out a data contract in March at MTN in Blue Route Mall. I requested a sim swap to be done from an fnb number. 2 weeks into the contract I realised no one could call me as it would say "the number you have dialed does not exist." I then contacted the agent who assisted me and he managed to work something out, however I am still unable to receive calls from the FNB network. Its been 3 months of contacting mtn and still no resolution to this one network not being able to get through to my number. I even contacted fnb connect and they mentioned the problem is not on their side. I am so frustrated.