Complaint about shoddy service

Cell C closed shops and they conduct business telephonically. I have called several times regarding a simcard I wanted to do a simswap on. I haven't been utilizing the service for a while because I lost the simcard. They are refusing to activate the card on the phone yet they do not have shops in and around where I live. I am paying for a service I am enjoying. It's been months and no one seems to care. Each time I call I get a promise that some supervisor will call but nothing comes through. I am distressed big time.