No Coverage in my area, returned router and cancelled contract. Still being billed monthly

I got an LTE router on contract from CellC about two months ago. I received a router, but when I tried to use the internet I was unable to. Cell C then sent out a consultant to come help with the router. I was told by the consultant that there is no coverage in my area. I have already been billed twice for this and I havn't received the service that I'm being billed for. I would like them to cancel the debit order and refund me in full. I want internet. I don't even have the replacement router yet that CellC promised to send me, was supposed to be an LTA router with better coverage according to CellC.