A simple way to avoid issues like this is to always generate a virtual card for each purchase, and then turn the virtual card off the moment the transaction is completed. You can do this through Netspend prepaid cards - you just open their site in another tab, generate a card with two clicks and turn it off with another two clicks. It costs nothing and the whole process adds about 1 minute to your purchase. I do this for every "free" trial I take on - if I like the service, then I will consciously make the decision to change the billing to a real card. No one gets to make that decision for me.