Refund

I took an upgrade with Cell C in October 2020, then I returned the handset still sealed in the box since it wasn't what I was looking for. However, Nove and Dec 2020 I was billed for the hand set which I handed back. I have on numerous occasion asked for a refund but to date nobody is willing to help me. Recently a query was logged and for some unknown reason it was closed without it being resolved. As it is now I have no idea who to turn to for help to resolve this query.