Terrible service from MTN

Greetings, i have had an absolute terrible experience with my MTN Contract, its been months now trying to resolve this issue and nothing yet...Please help me, i had an MTN contract and i could not pay them when covid hit as we were not getting paid, but when everything was back to normal i then asked for a balance then paid them off instantly it took them a whole month to allocate the payment and then i was told that am still owing because they didn't get the funds in time and every month they are adding an amount and i was not told about this ...please please help me i am so angry i cannot be paying for a phone that i dnt even have, your prompt response will be highly appreciated.