It also depends on the profile you were connected to when you went into an area of no coverage . If you were on USC and drove into an area without USC , sprint or TMobile coverage , or a USC roaming agreement you ' d be up the creek . If you forced it to the TMobile profile , and TMobile had a roaming agreement with att and service there , toy would then roam on att via the TMobile profile . Fi doesn ' t auto switch you to a roaming carrier that isn ' t directly associated with the profile you ' re currently connected to if this makes sense . It is a primary reason of having signal spy or the like on your phone , for these rural out there I need to connect to any roaming agreement that is in place . Signed , someone who lives in Maine and requires this feature at least once a week due to work locations .