Cancellation of expired contract

I have been trying to cancel my expired MTN wifi contract for the past 3 weeks now with no success. I had a wifi contract which expired 11 Dec. 2021. I was paying R199. When I called them in October to inform them that I would like to cancel the contract when it expires they told I should not worry as they will put it on month to month. Little did I know they will now debit R320. I went to the MTN store and was told it can only be canceled telephonical. And then I was informed I owe R650 now in January which I have to pay before they can cancel the account. It has been 2wks since I paid the money but until now my contract has not been canceled, instead it has been loaded. Every time I call them the call drops whilst I'm holding or talking to the consultant. I'm further up with MTN. Can you please help me to cancel my expired contract with MTN.