Cell C is the worst when it comes to service !!!

Worst experience with Cell C. I cancelled my contract last year and was charged for things I don't know after the contract ended now I am being sent sms's stating that I owe. What exactly do I owe when I have fully paid my contract and asked your employees to cancel the contract and it wasn't done. No one follows up on complaints. May you get to the bottom of this and also share your complaints process, as a consumer nothing has been shared with me in terms of complaints process. Your employees do not even respond to customers on email