Vodacom contracts are a ****!

Vodacom does not want to cancel my contract and my contract is over, they've tried to convince me to upgrade and I've declined. I even called them a month before the contract was coming to an end to let them know that I want to cancel and yet they haven't cancelled,. They go back and forth with me. I don't know if I should seek legal advice. They have been trying to deduct money from my account