First things first.. :D:D WELCOME TO WPCENTRAL :D:D
ill tell you how to look it up :)
give a man a fish , he eats for one day , teach a man to fish he eats for a life time :)
1. look up what Network / frequency your carrier is using. ( CDMA , HSPA(+) , LTE , GSM )
2. look for a WP7 that matches does Specifications.
3. order that bad boy!!
For example the SAMSUNG FOCUS S: be careful, its not Because if it has a SIM card that it work with all SIMs
GSM 850 / 900 / 1800 / 1900
WCDMA 850 / 1900 / 2100
does are the specs , if your carrier support does frequencies ( 850 , 900 , 1800 , 1900 ) your good to go.
Even does does Frequency are on GSM it would work on HSPA as well... but not necessarily on LTE because the technology is different. ( dont need to worry about LTE right now doh , we dont even have one :P )
Hope this helps :)