I am considering T mobile servcie and the Samsung S105 or perhaps a Nokia 3390 I know the the 3390 is a 1900 Mhz phone only (T mobile operating freq.) and the S105 is I guess tri band, as to cover the lower GSM freq also. I have been seeing some posts with regards to "unlocking" the phone. My question is: If I buy the S105 for T mobile service will it operate ONLY on 1900 Mhz ? Do I gain anything by unlocking the phone, or would this only cause to potentially corrupt my billing, if the phone were to lock onto another GSM carrier ? I don't travel globally, so this is not a concern, or a reason. If the S105 is only going to work on the 1900 band only, there seems to be little reason to spend the extra money, and rather just buy the Nokia. I have been told that even though 3390 is a "low end" phone, it is one of the better ones for T mobile service, at least in that price range. The extra bells and whistles, color screen, etc., of the Samsung don't interest me that much, as I want the phone for basic voice communication. Also, I have been seeing information that T Mobile is now signing more roaming partner agrrements with I believe ATT and Cingular (as they are migrating to GSM) Does this mean that the S105 would be to my advantage, as it would operate on these other carriers 850 band as well, and therefore perhaps provide me with more thorough coverage ? Or, will these agreements, where they exist, only be with other 1900 MHZ band systems ? Thanks to all who may enlighten me on these network issues.