bad service and they don't care

I complained a few months ago as I was getting no contact with regards to my account. My original contract was past the 24 month mark a long time ago. I was upset, however over looked the additional charges, and raised a complaint to get someone to assist with an upgrade. I was attended to almost immediately however after the application I have had no feedback. I would now like to have all my money reversed from when the 24 month period expired. As I tried to give them a chance to assist me, but obviously to no avail.