Only real way out now would be to try and void the contract, which would likely require legal support, which would cost more then just paying off the contract.
You could try and use the good old 'unconscionable contact' saying they forced you in to it and you weren't really aware of what was going on, then they made you sign some piece of paper that they didn't even give you the chance to read. I'd imagine A LOT of ppl have tried this on them though and they'd be well aware of how to confront it.
Otherwise, say you were drunk or high when you signed it, once again that's going to be pretty hard to prove.
Otherwise umm..... close the bank account that the membership is attached to, open a trust fund in the middle of nowhere (Nevis, Bahama's, Switzerland) and tell them the money for the membership is being transferred from that fund, it should arrive any day now! Then just keep saying you have no idea where the money has ended up and you're confused and stressed, and the pressure they keep putting on you is causing you to have a mental breakdown and they better stop harassing you or you will sue them.