There are a number of posts describing the use of a foreign iPad on AT&T with prepaid Visa cards and I managed to get it to work with my own credit card, so I thought I would share my experience. I bought my iPad 3G in Canada, and put in a Rogers SIM (I didn't end up activating it before I left though). When I got to the US, I went to an AT&T store (corporate owned) and asked for an iPad microsim. I believe they are supposed to be $15, but the guy there was nice enough to give it to me for free. At first it didn't work, but I realized all of the APN settings have to be blank to make it work. Once I selected to view account settings it opened up a form to sign up for a data plan (no sync required!). The form asked for my name, phone#, email, password, credit card#, and billing address. I entered my Canadian AMEX, and the billing address of the AT&T store where I got the microsim. I selected to use the same service and billing address (I didn't enter my real billing address). I sent off the info and got a popup text saying that the payment is processing. About 5 minutes later I got a message saying that the plan was successfully activated. The internet still didn't work so I restarted the iPad (holding down the sleep button and turning back on), and voilà! Internet was on while I was driving down the highway. I think some of the issues with using a foreign credit card may have come from people trying to enter a foreign billing address, or maybe AT&T just made a running change regarding foreign credit cards. Now all I have to remember to do is cancel the service before I leave. If anybody else gets this working or if anyone has a question, post a response. P.S. I am writing this on my iPad over AT&T 3G.