New Contract, endless problems

Ever since I have done my upgrade with MTN on January 2015 I have had endless problems with my account. I have to phone them (808 for customer service and hold for almost an hour before anyone bothers to answer) every damn month regarding my account. My account has been paid like it does every month what the owing amount was, Now my line has been suspended because they say I still owe R 244.00 but when I phone them I am in a credit for May and June 2015 both for the amount of R 244.00. I was told to pay R 588.43 and I did on 3 July 2015. When I received my July statement it says I owe R 1489.50 of which is impossible if the account has been paid in full every month. I WISH MTN CALL CENTRE STAFF WOULD GO BACK TO SCHOOL AND GET TAUGHT HOW TO DO THEIR DAMN MATHS AS I AM GETTING SICK AND TIRED OF ALL THEIR RIDICULOUS **** AND THEY ARE ALL UN-EXPERIENCED IDIOTS. If you get one out of 500 who actually does have brains and know how to use them it is a miracle. When asked for a rectified statement you never get it because their accounts for that month has already closed. I WISH NASHUA MOBILE NEVER CLOSED!!! I NEVER HAD SUCH PROBLEMS WITH NASHUA...EVER!!