Impossible to cancel contract

Trying to cancel my contract for two months now..... I keep being debited R650 for R200 airtime. When you phone the number to cancel the contract they spend a fair amount of time trying to convince you to upgrade....... even whem iade it clear i dont want to. Saw I was getting debited again this month and phoned the number.......... 3 times they have put the phone down on me. Stay away or pay as you go