Unable to get a contract sim swap even though my account is paid.

have been trying to make a swim swap , and ive been told that my number is blocked at this point i dont know what to do, when i go to the store the consultants say they cant assist , i need to call MTN for the past three weeks i have been going to pillar to post , trying to do a sim swap and mtn doesnt wanna help me , they say i should go to the store when i go there i get the same results.