MTN containues to charge after cancelling an expired contract

My contact expired at the beginning of December for Number. Immediately upon expiry, I called MTN and requested my contact be cancelled. I was given a Cancellation reference number *** . On the 15th of December my account was debited again by MTN. On 17 December 2020 I called to query the cancellation and was given reference number 296 809 653.

My account was again debited in January, again in February and again in March. I have called the MTN helpline and sent numerous emails to *** and messages from Facebook Messenger without any success in resolving this matter. I keep getting a standard response from MTN about the delay in resolving the matter but nothing has been done and they keep debiting my account for a huge amount which is a financial strain.

I immediately want a refund the amounts I have been debited after I cancelled the expired contact. MTN must also stop debiting my account