Bad service from MTN

Hello Peter. Since October 2020, I've been trying to cancel a cellphone contract with MTN, however, to date the matter is still not resolved. After getting confirmation from their consultant that the contract is cancelled, I kept receiving invoices and they continued to deduct money from my account. I contacted them telephonically, but I was sent from pillar to post. I then resorted to communicating with them on email requesting them to pay me back the money they deducted from November. They only called me back in January 2021 to confirm cancellation and also to confirm that I'll get my money back. To date, I haven't received my money back and MTN continue to send me emails demanding payment. I have copied their complaint's department but nothing has happened so far. I would really appreciate your assistance on the matter. Thanking you in advance.