Network and sim card

I am absolutely fed up with MTN and the MTN call centre (809). My incoming calls do not work. People have smsed and whatsapped me to tell me my phone is constantly off, when it's on! All my accounts are up to date and paid! I have phone atleast 20 times call centres to address the problem and all they have done is refreshed my network and SIM card and said it would work which it hasn't. I decided to do a sim swop to see if the problem would still happen and it did. Mean while doing the sim Swop they never refreshed my SIM card as explained to me by a call centre consultant. No one has a clue what is going on and can't give me an answer why I can't receive calls!!! I am absolutely furious as I have wasted my time calling and going into MTN STORES! And still as I right this my incoming calls won't go through to my phone! I was then told my account was suspended and then reactivated, who gave the right to cancel or stop my incoming calls! Especially when all my accounts are up to date!!! I am honestly disappointed and appalled at MTN SERVICES! Something is wrong and NOONE has a clue what to do!! I want to cancel my contract!!!! I would love someone to try and resolve this matter! ASAP