WILL NOT PAY FOR SERVICES I HAVE NEVER EVER USED

I took out a gym membership with them in 2013 and i have never used that gym i called them 2014 when i started to work to cancel i don't want that membership anymore, mind you i have never used that gym i don't even have a membership card for that matter i have never been there or used any of their services , the agreed to cancel few years later they keep calling me that i owe money for that gym i told them to hell with that as i will not pay for something that i have never used. they should stop harassing me with stupid phone calls that am owing, i will not pay them and if they want to take this matter legally am up for it