Cannot cancel contract after 24 month period!

My contract expired in March so I sent emails to [Email Removed] with no response received for weeks. I contacted the call centre on numerous occasions while being put on hold for 30+ mins on different occasions. Spoke to a consultant to apparently processed the cancellation but no feedback to confirm as the consultant advised they will be in contact within a week to confirm cancellation. This is a data sim I've had with mtn for 2 years, I had been considering an upgrade on my other contract but due to the lack of consideration and poor service I will not continue my relationship with this service provider and will look elsewhere in future. It is incredibly frustrating considering that they are extremely helpful during the sales period however totally ignores any service after that. The customer service needs serious work. I can't be paying for a contract that has ended and do not need, I will not pay any further charges as I have already given my notice as this contact has ended. I would appreciate feedback regarding this as I will not call or pay anything until I receive a call regarding this matter,