We sell a lot of unlocked phones that are brand new in packaging.  The majority of them will be in OEM boxes from the manufactuer like Motorola or LG, but sometimes they will be in boxes from a carrier such as Cingular or T-Mobile.  There are a few differences between the two types of phones, but also several similarities.  I will try to explain the best I can below so that you can understand all about them even if you had no idea beforehand.

First of all, there are dual, tri, and quadband phones.  The main bandwidths in the US are the 850/900/1800/1900.  The majority of phones in the market these days are either tri or quadband phones.  To simplify this for you, you can assume that triband and quadband phones will work with T-Mobile and only quadband phones will work with Cingular and AT&T.  There are exceptions to this rule mainly being if you have a triband phone that has the 850 bandwidth then that will work just fine with Cingular and AT&T.  The 850 band is needed in most areas for Cingular and AT&T to have full service.  Now, that being said, there are areas in the country where a phone without the 850 bandwidth will work just fine for Cingular and AT&T but you will want to give them a call before purchasing in order to verify if this is true in your location.

Secondly, OEM unlocked phones are going to be formatted to be basically a generic phone.  This means that they will be able to perform the basic functions of the phone which will work with all carriers on the GSM network.  This is the only logical way to make the phones as adding software for tons of carriers wouldn't fit on the phone, would take much more time to do and cost a lot more.  The good news is that you will be getting this phone for a lot cheaper than going into a retail store to purchase one.  In order to get the software needed for functions like the internet and texting to properly work, you will need to either call your carrier or visit a local retail location.  We have sold thousands upon thousands of this type of phone and I can count on one hand the number of times that customers were charged for having this software downloaded onto their phone.  They have specified software for these functions to operate properly on their system.

Thirdly, unlocked phones that are already branded and loaded to a carrier such as Cingular or T-Mobile will already have that companies software on the phone even when it is unlocked.  The phone will most often also have the logo or name of the carrier somewhere on the phone.  If you are buying an unlocked Cingular phone and currently have Cingular or AT&T for your service then you won't need to do anything further to make the phone fully functional.  If you are buying an unlocked Cingular phone and have T-Mobile for your service, then you will still need to have your carrier's software downloaded onto the phone.

Well, hopefully this helped you figure out what you are getting into when buying an unlocked phone for the gsm network.  It really isn't all that confusing, but not having a clue about the terminology or phones themselves can be intimidating.  If you see anything that needs to be revised or added to this guide, please feel free to let me know.