I offer to you a German Ortel prepaid sim-card. If you want to spend your vacation in germany it is good to have a german sim-card with a german mobile telephone-number. There is a balance of 7.50 EURO on the sim-card. And thats are the points for a German sim-card:

No roaming-costs in Germany for calls to mobile-phones and to the fixed  telephone network.

If your friends wants to call you on your german telephone-number tell them the number before you start your holidays. You will not pay any charges for the call of your friends to the german number when you are in Germany.

No roaming cost within the European Community for data and National calls.

Do you still have any questions, do not hesitate to contact me via the ebay-system.