Cancellation of contract

I took out a contract online with telkom for Wi-Fi router. I received the device quite quickly but the sim card had not been activated. I tried for over 3 weeks to get the sim card activated, this was after they had already debited my account. I then told them I want to cancel the contract because I don't want to pay for something that I can't use. I have been trying now for nearly 6 months to get them to cancel the contract after I have sent them all the forms they requested from me. If I don't contact them and follow up on the contract I don't hear a word from them except to tell me my account hasn't been paid. I am really disappointed with telkom. This is unacceptable.