No action on request to call centre

Called more than a month ago to change my ADSL contract. It was not actioned by the agent. When I called a month later it was still not resolved. The supervisor had gone home and would call me back the next day. It has been more than a week since that call!<br> I have been charged for Years for the Fastest bundle ADSL but have only been receiving the Fast bundle. I am owed a huge credit I think?