Refund and cancellation of contract

Telkom is very easy to get a new contract but is flipping difficult to cancel one. We sent emails for cancellation more than 5 times with no reply and they were busy deducting from our account and we disputed. Now this disgusting Telkom sends me a letter of demand after they deducted thousands of money from our account that we can’t dispute. I want my money and please cancel your stupid contract cause I don’t want it anymore…