Please convert my number to a prepaid?

I’ve been with Cell C for over a decade and have mainly been happy hence the 4star rating. I’m just struggling to cancel my contract. I’ve sent an email, no reply or acknowledgment. I got a call to offer me an upgrade and I advised the consultant that I want my number changed to prepaid as I paid off the outstanding balance so she said she would put me through to the cancellations department but instead the call was disconnected. Please can you cancel my contract and change my plan to prepaid until you get new phone stock?