Several Possibilities to say that in German

one is: 'Nicht netzgebundenes Handy'

Feel free to mail me if I can help

Yeah, the old "handy" thing. ;)

Actually, you'll probably be able to get your hands on a cheaper phone in a regular phone shop - find one that has lots of different brands so you have a choice. Depending on what you look for, unlocked phones are on sale for 30 - 50 €.

If you search on the internet, I'd go for "[Handy] ohne Vertragsbindung", "[Handy] ohne SIM-Karte" or "Pre-paid handy".

Well the advice Hilmar gave you is good. I do know that you can go to shops as well and sometimes get them used as well and activate the phone. I know I was able to use my US cell phone/ Handi in Germany ONLY after I got a new simm card for it that worked there. I had to prepay for it and insert and replace old Simm and you are good to go.

If you are on vacation only this is one way to go as is renting one from the airport or a Handi company as well.

Again try Hilmars link first and you have this as back up info just in case. IF your US phone is NOT a Simm card than you will not be able to convert over their. The only company I know of in the USA that works here to Germany as well as from Germany to the USA is T-Mobile network. Most US Cells/Handis do not allow you to call to europe unless you ask them for an international plan. We do not pre pay for ours or have them auto deduct from our banks as you do. In the US we generally pay a bill for what we used and that cycles every 30 days, yes you can get pre paid ones still.

I hope that is a little extra help on top of theirs!