contract ended may BUT IM STILL BEING BILLED

When I called the gym, I was told that once my contract ended it automatically rolled into a month-to-month membership. I explained that I never attended the gym for long, and due to being pregnant I made it clear that I did not give permission for my contract to be renewed. Now they are insisting that I must first pay the arrears before they will cancel my membership. If this is truly a month-to-month arrangement, and I have not swiped my card or used the gym, how am I being charged? This feels unfair and misleading, and I am requesting immediate cancellation without being forced to pay for services I did not use or authorize.