Bad service

I went to mtn mall of the north polokwane to pay my monthly installment.The consultant advice's that i can upgrade my contract because its due.Decided to get a phone.But after a month i got a message that iam owing mtn R6000 for early cancelation.I did not cancel anything .I called mtn several times and my issue cannot be solved.I went to the store over 3 times still the manager and the consultant are just apologizing saying its their mistake and they are not helping.I cant do anything with my contracts because this issue has blocked everything.I am tired of calling mtn and when i call the store they just keep me waiting without getting back at me.Iam suffering because of the bad service that was entirely not my problem