CSS Credit Solutions PATHETIC service, harassing behavior

CSS continues to harass me for a Cell C outstanding account and I DO NOT HAVE any Cell C account. I have been to police, Cell C for the past 2 years informing them that I DO NOT HAVE an ACCOUNT with CELL C. Everytime I need to send all the documentation through without any reply from them. Next thing...another call from CSS Credit Solutions. I have left numerous requests for a manager to contact me, no reply.