madra31 wrote:
There are two types of unlock, domestic and international.
If your phone is domestic sim unlocked it will work on AT&T and TMobile and their respective sims.
That is not really correct. Unlocked is unlocked, and can be used on any GSM carrier in the world. You may be confusing it with selective locking. A phone sold by some partners, such as Best Buy in the US or Carphone Warehouse is advertised as "SIM-Free," but this is a misnomer. What they are selling is a phone that can only be used with a small number of carriers, and further, will lock to the first carrier it is used with. As those carriers are in one country, it may appear to be a domestic lock. But it is really not unlocked at all. And to further confuse the matter this is referred in the industry as "FLEX policy" rather than it really is UNflex policy.
Sprint at one time sold phones that were locked to Sprint if used in the US, but were unlocked Internationally. I don't think they do that anymore.