MTN contract cancellation

My contract was due January, from December was trying to reach their Retention department to notify them that they must cancel it. No ones answering their phones. I sent them an emails still no response. On February they load the Data then telling me I’m on month-to-month contract. 10 gig for R539. I contact customer care they also failed to assist me. And I notify them that month end should they debit I will reverse the payment. Not they’re telling me that should I fail to pay that amount they won’t cancel my contract instead will keep on going up. Might end up paying more. Who’s fault is that they don’t answer their calls and emails. Clearly this is not fair as a consumer I can’t pay 10 gig for R500 while there’s thousands options to save in South African. Please assist me with this matter