Paying for service not recieved

Your sell direct team sold me a router and service was fantastic. Problems started after your call center activated my sim. Ever since then the router has never worked and every time I call your call center they tell me i am using the data but I have never connected to the device as it never worked. I know I am not crazy as I know the device never worked yet last month I was billed over 400 for using this device. This is my 3rd product with Telkom and I am so disappointed this time around with the service received. I walked into your Eastgate store to get this contract cancelled and no one can tell me how much to pay instead I get a form to fill and I must bring my ID and still e-mail it myself, totally disappointed.