That is a fluid situation. 2100 MHz band 1 is the most used, Europe, Korea, Japan are biggest users. ATT is 1900 PCS band in USA. T-Mobile just started up the AWS 1700/2100 MHz band in U.S.
ATT in U.S. is converting their 850 MHz low band holding to WCDMA. Some operators in Europe are converting original 900 MHz band.
Does each operator provide information on which bands it uses in each country it operates?
Lets take Orange as example.
How can you know which bands it uses in a certain European country?
Like, how can you know if it uses more bands than band 1?