MTN SUSPENDED MY CONTRACT

In mid-end of April 2018, I went to MTN in Hatfield Plaza to open a new account. Everything was approved and I got my contract with my phone. It was not necessary for me to make payment end of April as I only had the phone almost two weeks at that time and I was informed that my first deduction will only be at the end of May 2018. About two or three weeks ago my sim card stopped working. Every time I try to make a call it says that my sim has been suspended. I tried to contact MTN with no avail because it requires me to add my cell phone number and it keeps saying that the cell number is incorrect. I also tried going back to Hatfield Plaza's MTN but they moved away. I just want someone to contact me and tell me why they have suspended my sim card. I don't think it is fair to expect me to pay end of May if I haven't even used the sim card because it is suspended for some reason without informing me of same.