Don't American mobile providers strongly suggest another network (drop you) when you live or mostly use your phone in an area for which they only have roaming coverage (through an agreement with a different company)?
Yes, I have known several people who have had this happen. One friend had a couple of kids away at college on his family plan- the company sent him a letter that they were canceling the 2 lines his kids used out of state (roaming), so he switched providers- they then wanted to charge him for breaking his contract! He sent a copy of the letter canceling the two lines and explained that they were the one canceling the contract.