MTN *****ing money

MTN Home Router I was charged a fee for December 2023 which was not communicated to me and MTN refused to correct this. I called to cancel the contract and was refused help to cancel it and was told to go in store as the device must be returned and cancelled in store. I went in store to return the device and called MTN to cancel. I called in store. I was assured that before I left the store that the cancellation was done. My account was debitted this weekend and MTN refuses to refund me for the month and confirm my account will not be debitted again.