Cancellation nightmare

I have been trying to cancel my contract for two months. Have been sent from pillar to post. My data contract was supposed to have ended in March and phone contract should have ended in June. Each time I call cancellations I am being told the end date is wrong needs to be fixed and I am promised an escalation and someone would get back to me. Two months later I am still being charged for a non-existent contract and cancellation not processed.