cell c fibre very bad service

I am only writing this complain as i dont know who to complain to anymore. I had a fibre line. I moved. I gave my notice. I paid per the mail that was sent me. I have all of this on numerous emails. Yet cell c is still debiting my account. Every time i reverse the debit order it costs me. Collections department phone me once a week. i tell them the story they promise to sort it out and phone back they do not. Please can somebody help this is ridiculous. How can such a big company have no communication between departments. i dont think i will ever deal with cell c again.