MTN overcharge

Hi. I have been a huge fan of MTN since early 2000. In 2018 I took a data contract which run for 2 years. I cancelled it in November 2020. However upon the cancellation I was charged almost R600 and still today I dnt understand why, immediately I reversed the that amount and MTN suspended my account i.e couldn't make calls. I then inquired at which I was told I must pay the R600 for them to lift the suspension to which I did pay. However they continued debiting me funds for the subsequent months including November up until February even though the contract was cancelled and I ddnt receive anything in return. Each they would debit I would call to inquire and was told it was a mistake in their part it won't happen again and yet it kept happening. Eventually the debiting stopped. However,in July 2021 I received messages and calls stating that I must R283 wich was due in my account,I was really surprised and confused since my contract was cancelled more than half a year ago. I went to local MTN outlet to inquire about it and was told I had outstanding amount of R283,still could get satisfactory explanation why I was supposedly owing R283. I paid anyway. My point is since I cancelled that contract I paid more than R1000 which still to date I dnt know what for and I am not sure if one day I will get another call saying I owe them x amount. I am really hurt by MTN. *** Emmanuel