I use Verizon (just rated best in cust. sat. although they all suck to some degree) They do not offer any GSM phones to my knowledge so overseas travel could be an issue, although some countries are listed on their site and in their plans. I had great service in Cabo and Moab and very few no service areas in the 4 yrs I've had their service. Free calls to other Verizon phones but then most companies now offer that. Good luck!