My name was handed over to nubet collection

Good day, Hope all is well I have a contract with cell c my problem is that there's two cell phone under my name but the other cell phone I'm not using it, it use by someone else. Under this contract there's two different people which is me and that person and we using different bank Acc which is nedbank and fnb l. So cell c doesn't received debt order on fnb so they keeping on calling that they do get money from fnb and I'm not using fnb. Pls help m

Regards Happy