Cancellation of my contract

I was told by mtn to call back on the 2nd of april to cancel my contract. Yet again we have to keep on phoning back to mtn and try and get trough after an hour i got trough to reception and then she tried to contact the supervisor and can not get hold of any one in that dept. Mtn must not come back with excuses that they are busy. Vodacom answers within 5min or have a call back system. I refuse to pay mtn on my account as i have been trying to cancel my contract since the 23rd of March and this will again take a week for mtn to respond back.