Very bad service

I get calls regularly from some debt collectors about an amount I owe Markham and requesting payment. I pointed out to them that I don't purchase anything at Markham for months now and I paid every cent I owed them. Apparently, I am now being for a magazine that I indicated I do not want and that I don't even receive. That was years ago. One call center agent advised me to call Markham's accounts department and ask them to reverse the charges. I did this and spoke to Lucretia weeks ago and she promised to sort it out. No luck, so I have to call again and go through the lengthy choose this, choose that options again. So I end up with her colleague and I think the name was Felicia. She said Lucretia was busy but one of them will definitely call me back before the close of business. That was a promise she swore they would fulfill. A week has since passed. No call from anyone. So now my credit record is being affected because Markham is so desperate to make money that they charge me for some stupid magazine which I don't want and which they even get debt collectors to track me down for and hunt for money. I don't buy anything from them anymore. I would like to close my account but can't do so because of this issue. Their ***