Originally Posted by Dubdub
The 8830 is CDMA in US and GSM elsewhere, You cannot use it on either ATT or T-Mo as GSM is a totally different technology. Plus Verizon and Sprint currently only allow their own branded phones on their networks, i.e. no Verizon phone on Sprint and vice versa. That is slowly starting to change, but don't bet on being able to do it, even if it is the "same" model number.
The GSM Technology is the same. Its that the bands supported by the 8830 (900/2100Mhz) is NOT what the AT&T, T-Mobile, West, Rogers, or Fido networks use in North America ... they all use 850/1900Mhz for GSM/GPRS/EDGE (when it comes to 3G - then that is offered in Blackberry devices this side of the pond - then T-Mobile is the exception to those bands ... using 1700/2100Mhz).