is that phone sim unlockable ? Wanna be on whatever network (carrier) i want.
I don't think you'll be able to get on Verizon, Sprint, and GSM carriers with the same phone. Some of the Verizon "world" phones, I've wondered if you can take them to ATT, but I think you would have voice only.
Best you can do in the US is get a pentaband phone, and then you can choose from ATT and TMo, and any MVNO's that use them.
I believe the main ones are the GNex, T-mobile's version of the S2, and the HTC Amaze 4G. The problem with the TMo ones is they are ~$550 new off-contract. The GNex presumably just has less markup (Amazon Wireless shows the VZW GNex at $650 off-contract, Sprint at $590).
With a CDMA phone, you pretty much buy a Sprint one or a Verizon one. There are MVNO's for both, which may or may not be easy to port the phone to (Page Plus Cellular on VZW is easy, porting a Sprint phone to VM or Boost, not so easy). As far as I know, you can't get the same device to work on both.