Bad business

Almost 4years ago I took out a month to month LTE contract out with this company and they told me that I should get a certain router for there simcard to work and I went and spend money on the router,after buying the router,the sim didn't work on it and I was in contact with supersonic and I went on and cancel the whole thing because it was a back and forth thing. Now after a few years they want me to pay for something I never used and cancelled on top of that...