30 day notice gym membership?

My wife started taking classes at a new gym a few months back. She started paying on a per class basis but they later opened it up to enroll for classes monthly. She canceled her membership and they told her they required a 30 day notice. Now she states she was never told this and never signed anything. All she did was give them her cc info and they started billing her.

Its a local gym and i've contacted the person who handles this twice about the 30 day notice. We told her that my wife was never told, nor did she sign any paperwork stating this. I even told them that if my wife did sign something, I would like for them to email me a copy of this for our records.

So far, no response after two tries and the billing date is tomorrow. Can they charge me another month if we never signed anything?