Thank you for your quick reply, I'll check the documentation from my BES Download!

The Blackberry is not from T-Mobile, however, it is from the german provider O2.
I already tried my T-Mobile and E-Plus SIM Card, but it wasn't recognized..I think the blackberry was simlocked from O2 to prevent other SIM cards from working with this unit.

Is this common practice with Blackberries or is there some way around this?

In any case, thanks alot for your effort!

Dominik