Unexplained debit orders after cancellation of cell phone contract

This needs a negative star...

I cancelled my MTN contract and my number was migrated to prepaid. On 20 February I paid R 3 455.00 after contacting 808 to confirm the amount outstanding to cancel the contract, which was the above amount paid at MTN store in Harrismith. On 26 February I received confirmation that payment confirmation was received at MTN and my number has been migrated to prepaid. However on 15 March, my bank account was debited with R 1 348.63 from MTN, of which I don't understand why because I settled my account with MTN last month. As far as I know after my communication with a consultant at 808 and MTN store in Harrismith, that was the only amount due of which I paid, including penalties for early cancellation.

My account was debited with R 1 360.13 (an increase from last month) again this morning by MTN, after I cancelled and paid off my MTN contract in February 2018. So my email in March was never attended to the same thing happened again today with an unexplained debit order on my account by MTN.

What does one have to do to get service from MTN customer care (if it really does care) because the amount seems to be increasing, or do I have to wait until the whole salary is debited?

The incompetence of MTN is going to be their downfall, especially in terms of customer care.