Can't receive phone calls

I've been following up with MTN regarding the same issue since my contract was moved to prepaid which is end of June, and still no one is able to fix the fact that I can no longer receive phone calls. The most annoying part is that even though my number is now on prepaid I can't port out to a different network. When is this issue going to get fixed. I've been calling MTN, emailing them and still no one is able to assist me and I have to keep waiting on some department to get back to me. How will you get back to me if you can't call me? This is becoming ridiculous!!!