Poor service from MTN

I have a contract with Mtn. I called the call centre sometime in April 2015 to cancel and i was advised that i will receive a follow up call to ensure that the cancellation was done. Up until this day i havent received any call from them. I have called several times but no one is answering. Sometimes i hold for 30 minutes and the call gets cut. Why do i need to call the call centre to cancel my contract wheres i took it at the branch, this is poor service on MtN and i am absolutely disappointed. I am definitely considering switching to other service providers.