On your profile where you get asked questions like whats your fav movie and so on. Replace any answers you have already left with offensive language which in turn will violate their terms and conditions and they will have no option than to close your account. As for getting a refund good luck.

Use a prepaid card with limited funds, so that they can't continue to steal your money.

I got my credit card to stop letting them bill. I noted to them that I tried in good faith to stop eharmony's almost impossible-to-cancel auto payments. Credit card stopped future payments.