My daughter made a very similar mistake a few months ago. Thankfully she was able to get in touch, argue it on one of the terms, get it canceled and refunded (eventually). It could be worth a try if you can get in touch with them some way. It depends how generous they are. Sometimes our most painful mistakes are the ones we learn from best. I don't even sign up for these things now if I can't risk forgetting and a payment going out.