Shocking, unacceptable service from MTN

MTN SA - I am disgusted at the shocking service I have received from MTN. I have been a customer for over 20 years but am experiencing the worst treatment ever. I had a sim / data contract which came to an end. I did not want to renew. A representative spoke to me about a router which I was not sure would be suitable for me. I consented for it to be delivered to me for me to see it and then decide if I wanted it or not. I was assured I could cancel within the 10 day cooling off period if I wanted to. I subsequently phoned MTN to cancel and I returned the router all "within the cooling off period". I also emailed and SMSd MTN to "cancel" sending them the return ref number. After many many phone calls and emails to their Retentions and Cancellations departments this matter has not been resolved! I am being charged every month since September (via debit order) for a contract I don't have and which I expect was to be cancelled. Eventually I was told that the matter will be escalated to management. It would take 72 hours to investigate my calls, emails etc to them, to apparently establish whether or not I did, in fact, request cancellation! What, really?! That was on 2 December. To day, 24 December I receive an email stating they will escalate my query!! Has it still not been escalated and is no attention been given to me. I am being kept on a round-about, in the dark. They are taking my money. This is an unacceptable way to be treated from a large SA company - I am a long standing customer. I would like to be reimbursed for all the debits to my bank account and a written apology from MTN SA. Cancel the contract MTN.