No response to complaint

I lodged a complaint with cell c around the end of April 2015, and I am still waiting for a reply. I have been give a case number. I have called the call centre on a few occasions and was promised someone would phone me back, no one has phoned me back. I have sent e-mails to customer service asking them to phone me, but no one has phoned. This is not good enough. The complaint was about a tele sells person upgrading my modem contract but what I have been given is not what he explained over the phone too me.