How can I use my unlocked AT&T phone in Germany?

First of all, did you buy an unlocked phone directly from an Apple store and you are just using it with AT&T? Is that right? I ask just because buying a phone contract free, and buying an unlocked phone, are different things. Even contract free, full retail priced iPhones bought from AT&T itself are carrier locked.

If you did get it direct from Apple as an offically unlocked iPhone, than any SIM should work, although depending on the network not all features (eg. visual voice mail, which is a network feature) may work if the network does not support it. I have read that Vodofone, T-Mobile and O2 do prepaid SIMs in Germany, but I would expect there are several others.

ATT doesnt sell unlocked iphones an wont unlock them - if you bought an unlocked iphone from Apple you should just be able to pop i a German sim card from a supported carrier in Germany

If your phone is locked to ATT - you would need to use somethin like Skype which will work over wifi or your 3G data plan

😕 ?? What's the problem? No one was rude to you. You said "AT&T phone" and everyone was just trying to be clear on what we were all talking about here. Have you any idea how many posts PER DAY appear on this site of someone outside of the USA with an AT&T phone asking about how to unlock it so they can use it wherever they are (the number may well be in the hundreds of posts, each and every single day)?

As mentioned, politely I would add, was that if it is unlocked, no worries - shop for the best deal in a local provider, get a SIM from them and you are set.

There is no such thing as an unlocked AT&T phone. If you have an AT&T phone that has been unlocked, then your phone has been hacked. Your warranty is void and you have forfeited all rights to support from Apple and on these forums.

No need to get hostile. You could have just stated that you had an unlocked phone. As for "AT&T was referred to because I know it is the type of phone used in Europe." I don't know what you mean by that. AT&T does not operate in Europe. An AT&T phone can only be used in Europe with AT&T service and an International roaming plan.

I'm sure you can see why what you said was confusing and resulted in the responses you got.