Well I am back from PRG, and thank god I rented a second phone as a backup.

For the most part, the Cingular Nokia 6620 would not pick up the Tmobile signal for my Tmobile Twist sim card. At one point, in the Tmobile shop, they got it to work briefly and I thought it was fixed, but then a few hours later it only would either bring up no signal or Oscar, etc. At the same time, there were 2 other people getting Tmobile signals from the same place without issue.

I did some checking on the Nokia site this afternoon, and the 6620 is shown to only work with ATT and Cingular. It also shows Nokia 6620 operates on 850/1800/1900 MHZ frequency range.

Other GSM phones operates on 900/1800/1900.

So was my issue perhaps that Tmobile in Czech Republic uses 900MHZ, but my phone only did 850MHZ? Is there anyway to see on a sim card or for a carrier which mhz range they use?

I'll need to figure out something again for the next Europe trip which actually may be in 2-3 weeks .