Maybe one of our German contributors (Andreas, Mark) can respond to this. Last August, I bought a Penney-Mobil SIM in Munich. It was actually T-Mobil service, but offered a lower prepaid rate with Penney-Markt. I had to call a number to activate it, which I did. The operator I talked to only spoke German, which was fine because I spoke enough German to activate the card. I used the address of the hotel I was staying in. He must have known from my accent that I was an American, but he let me activate it.
I then bought days on a €20 pre-paid card (the smallest available), which should have been good for eight days at €2,50/day. After four days of use, it told me I had to add days (four days would have been the T-Mobil rate of €5/day). Before I flew back, I called Penney-Mobil and asked them what happened. They indicated that somehow it had not been recognized as a Penney-Mobil SIM, but a T-Mobil SIM.
That was no problem because I still felt I had gotten my money's worth (on data), but she also told me that I, as a non-citizen, was not supposed to have been able to buy and activate the SIM, that they were only for German residents.
So my question is, can we use these prepaid phones, or not? Was that just a Penney-Mobil rule, or a German law (maybe since 9-11)? Are we breaking the law by using them in Germany.