I had a similar experience after a visit to Mexico. I picked up an ATT Mexico SIM card, and noticed that it still worked after I got back to the US. I bought

I had a similar experience after a visit to Mexico. I picked up an ATT Mexico SIM card, and noticed that it still worked after I got back to the US. I bought a new tariff each month for about $10 USD using Ding, and it worked great. The only downsides were that I had a Mexican phone number (I use Google Voice anyway, so just needed the data) and, more importantly, that all the customer support was in Spanish... I ended up ditching the SIM after about a year when the data stopped working when I bought a new tariff. Not sure how much this was due to my inability to navigate the Spanish customer interface vs. ATT cracking down on people doing exactly this.