Cancel contract now

I regret ever getting a contract from this stupid company. I have a data contract with Telkom and I’ve been paying well since with no issues. Until they tried debiting money on the wrong date and it bounced but I made sure I paid online. Since then everything is a mess they keep trying to debit more than the agreed amount. When I call they tell me about rejection fee I didn’t know nothing about and it’s not like I did it via the phone , no I went straight to the Hazyview branch n got the contract but they didn’t explain anything to me about that, now they keep debiting amounts I know nothing about. They debited R410 November and R623 last month instead of R210 and this month when I thought it’s okay now they want to debit R400, like really?For what. Please if it’s possible cancel this contract please I’m tired, I keep understanding and it keeps getting worse. ID *** k malapane