What is on my SIM?

The iPhone does not store anything on the SIM so changing SIMs will not affect any of the data or settings on the iPhone other than, of course, the cell carrier.

Regards.

Hi Oceanlady-

I've used prepaid SIMs extensively while traveling abroad, but just wanted to make sure that you understand that your iPhone must be unlocked if you wish to use it with a provider other than the one the phone shipped with. Your iPhone might be unlocked if you requested an unlock from your US provider and it was granted, or you might have specifically purchased an unlocked iPhone- though you don't mention either so thought I should ask.

Dave

I travel to Panama once or twice a year and use a local cell provider. Changing SIMs is no problem. You must first contact AT&T to unlock it. Sometimes after unlocking, you must activate the phone with the new carrier's SIM but doesn't effect settings.

Contact AT&T at: att.com/deviceunlock to see their requirements and fill out a request.

oceanlady wrote:

However, I was wondering, (just in case I can get it unlocked before I leave for Germany) if I remove the SIM here in USA, then use a European SIM for a few months, then return to USA and reinsert the original SIM, do I need to do a 'restore' from my most current backup? Or will all be on the SIM? No backup required?

Nothing will be erased from your iPhone by changing SIMs, though if AT&T grants an unlock you may need to restore your iPhone to complete the unlock and that restore would erase the iPhone, so you would need to use a backup. The unlock process is described in this article:

http://support.apple.com/kb/HT5014

Once you complete the unlock, then changing SIMs will not affect anything on your iPhone. Again, the iPhone stores nothing on the SIM.

Regards.

One last thing. If AT&T won't unlock your phone, you may want to check ebay and buy an older FACTORY UNLOCKED iphone for use in Germany. You can always put it back on ebay and sell it when you return. Good luck.