Fully check out the site before using your card online. Try to ensure you are purchasing from the "official" site of whatever it is you're after. It means some homework-research but it means protection & confidence for yourself. ukbobboy01 is probably a good person to ask about safety measures you should go through. It might be worth sending him a pm for advice. I too am reluctant to use my card online. Good luck with cancelling the transaction. At least in our country there are departments within the banks/credit co. that deal with these types of issues. So specify to them that it was a "scam"!
I reiterate, stick to the free version for now to ensure you can use it successfully & like using it. The differences between the free or basic version & pro are only subtle.