MTN bad service

I have a problem with MTN and its really frustrating me. I have a contract with MTN, I was listed as default but now my account is up to date. I was trying to buy a car and the bank declined. I called ITC to check and they told me I have a default of R310 with MTN. I called MTN since December till to date to update my account with no help. I call them like every day and its frustrating me. I am tired, I am also considering canceling my contract due to their bad service