Failure to allocate payments

My name is Zenani ***). I'm honestly not happy with the service I've received from MTN,I've been calling and emailing regarding allocation of payments I made since May but no response from them. Next thing they sent MBD to call and send me messages claiming I owe MTN. I called again querying this then one of the agents told me they have a backlog,you mean from May you couldn't allocate payments and yet you blacklisted me claiming you not receiving payments. I'm not happy at all infact I'm ****ed ,this is ruining my credit score! MTN doesn't value customers!!?