contract not canceled on specified date.

Contract was to be canceled on the 14th March after numerous calls from December from me requesting to keep my number and change to prepaid. Last payment was done by me on the end of February as I was advised. Apparently the contract would be switched to prepaid on the 14 March automatically. As off today its not done and I am expected to pay again for March coz the system didn't run the cancellation in march, it will de done in April. How do I know that the same system will actually run this time around?????? I refuse to pay for March because of autopage's system error. When I asked to speak to the manager I was transfered from pillar to post and noone answered their phones until I got cut off. I AM NOT IMPRESSED WITH THE SERVICE I GOT AS A CLIENT FOR ALMOST 8YEARS WITH AUTOPAGE AND NEVER ONCE MISSED PAYMENT.