I suspected as much.
I have a Droid 4 and have been to the UK a few times over the last few months. Ever since they did the ICS update the global settings are unlocked and it will take a foreign sim. You can pick up a pay as you go sim at W.H. Smith at Heathrow airport and it will work right off with voice calls but you will have to go online to get the settings for using data on the Droid 4 before it will work correctly. My phone always shows the sim as unknown but works just fine anyway. If you haven't used your phone globally before you will need to check your network settings once you have your new sim in and verify what network it is set on. You can top up as they call it, add more money to your pay as you go card from your phone or at many local shops or online. Hope this information is helpful.
The pay as you go I referred to was with switching out my sim card once I got to the UK. The pay as you go sim that runs on the Lebara network International Calls & Free SIMs | Pay As You Go | Lebara with their pay as you go you "top up" or recharge the balance available to use. You can check the data and voice rates on their website based on the country you want to use the sim in and it will tell you how much the rates are. You wouldn't get billed by AT&T also because you would already have removed the AT&T sim card and installed the Lebara sim which then the only charges you would get would be for the usage on the Lebara network. Hope this answers your question.
So far I have always used a simple cell phone with a pre-paid SIM for my visits in Germany.
This time I did not want to go without the smartphone functionality, especially Google Maps which I plan to use quite a bit.
So I had the German provider, Simyo, send me a microSIM replacement card, popped it into the Droid 4, set the network preference to GSM and could make phone calls within minutes.
For Internet connectivity Simyo send three text messages to my phone and those made the necessary changes to network settings after a reboot.
So far, so good. Google maps works, push notifications for Gmail work.
The only thing I'm curious about is what will happen when I go back to the US and return to the Verizon SIM again. Simyo did erase all the Verizon APNs, and it's going to be interesting to see if Verizon is as smart and easy in restoring those as it was to get Simyo working on this phone....
I'll report back in a couple of weeks if someone's interested....
Edit: Two weeks later: This was way easier than I expected. Returning to the States I just put the Verizon SIM back in, and everything switched back to the Verizon service. No problems whatsoever...
Sent from my ASUS Transformer Pad TF700T using Tapatalk HD