Bad client service

What a bad experience I've had with Telkom. Never will I recommend it to anyone, all they do is too push sales and not care about their clients needs. I've been trying to cancel my contract with them but they keep throwing from pillar to post. I visit the branch they can't cancel contracts and they refer me to the call centre but still can't assist, what am I suppose to do because now you are sending me an invoice with a crazy amount and who should pay for that? I'm so frustrated of you incompetences