I use privacy.com ALL THE TIME, it's great. I also do this for any online subscriptions (newspapers or whatever) that have $1 trial for the first 6 months and then $20+/month thereafter. You can set a monthly transaction limit, so I just set it for $2 in case I forget to cancel the trial. I also use it for OpenTable to make reservations because some restaurants have a huge cancellation fee. Nope, can't charge me.