Cell C Accounts Department Harassing Me

I have no contracts with Cell C. None whatsoever. ZERO, ZIP, ZILCH, NADA. Fortunately I still have the final statement from them with a ZERO balance. Maybe I should translate that ZERO in all 5 Billion of the official languages because they certainly don't understand SIMPLE english. They are sending sms's to my phone threatening to blacklist me and saying that I have been handed over for collection. This is not the first time Cell C has totally messed up and is one of the main reasons I now have decided to move to Vodacom after having 3 contracts with Cell C for Close on 10 years, maybe even more.