I have done a lot of paid trials so I was looking into prepaid cards, etc. I was playing to see if my credit card I use for all offers had anything that would give a virtual number for shopping online. I use an MBNA (now BofA) credit card and they do have a feature called ShopSafe. It generates a one-time number and expiration date for each online transaction you make. It also gives you the option to say that the number is valid and can be used for so many months. So, I'm going to use it and just say its good for a month...hopefully you can do .5 months so maybe these companies won't be able to keep charging even if they want to. Hopefully it works like I think!