Error with new SIM card

[ret-sop]

Hej guys,

I just recently moved from Germany to Sweden and I'm having a little trouble to replace my old SIM card. I have an unlocked Blackberry Curve 8900 running on OS 5 and sinceI replace my old SIM card with a new swedish one from the carrier COMVIQ I can't get it to work.
The SIM card works in other mobile phones (even other Blackberrys) but when inserted into my phone I can't call any number. Furthermore, I recieve the "Network congestion" Error each time I try to send SMS, although I have perfect reception. However, calling me is possible and I can also recieve text messages, so it must be something wrong with my settings.

Does any of you have a clou what could be the cause of that?
Thank you in advance