ok, i have an htc evo 4g with sprint. We have traveled all over the country and have had coverage everywhere either through sprint or roaming which is included in our plan. Someone told us about Boostmobile for no contract. My concern is coverage. Even though they say its roaming, will you get coverage in say, Montana? Also, we may be traveling abroad and heard you should have a GSM phone. We want to upgrade to maybe a samsung S4 but I don't think that is a GSM. I just read about the locked and unlocked. I'm a techie and still confused on what to do. Any feedback on Boostmobile would be great.