[kieller]

If it is a CDMA phone, and it sounds like it is, just like here in Canada, CDMA networks actaully keep all their ESNs on file, so if you were to try and use one CDMA phone from one carrier on another one, it will not work since that ESN is only good for the carrier that it was made for. Thats the nice thing about GSM, it only registers the SIM card, not the ESN of the phone, so if the GSM phone is unlocked, it's not carrier specific.