I forgot to say that all this "membership, "free trial" and "try it for free" offers are a scam too. First, the stuff never works but they keep charging your card after you cancel and ask for a refund. Or they just keep sending the crap and charging you after you cancel.

You call them up and spend hours getting it all straightened out and then they charge you again. It just repeats over and over.

You nor the credit card company can prevent anyone from charging your credit card once they get your number. They cannot be blocked so you have to get a new card with a new number.

If you use Pay Pal, they never get your number and you have to login and manually pay every charge