cancellation of contract

i have a contract with mtn,a simcard and i lost the simcard and stopped paying it,so after some time i was called by thier legal team telling me that the matter was ahnded over to them,i was asked to pay a certain amount which i paid,i got back to mtn ,they cant help me with a sim swap,cancellation nor upgrading my contract,i cant do anything and i see it leading to the same results again of bieng handed over to the legal team and paying legal fees too,i cant be paying for something i have no access to,please help me,i want mtn to cancel my contract i no longer want anything to do with them,they failed me as their customer because i tried to call but keeps ringing non stop.please help me out because now i cant take out anothercontract with any network because mtn has not removed the comment that my account is inareas and its affecting me now.