History: My well loved and well used old I-phone 4s was having issues of of old age (I tend to keep a phone until it dies, if it works, I'm good), when I went into the phone company and asked what phones were free since I had not gotten a new phone in ages they said I had to pay full price for a new phone and pay activation fee! I gave them my thoughts on the matter as a customer of over 10 years and changed my cell phone service.
My new phone is with Cricket, free LG Android phone, free activation, no contract and only $ 30.00 a month including taxes. It uses AT&T towers and has great reception.
I have been happy as can be for months until I asked them about using the phone when I will be in Europe in a couple weeks. The phone will not and can not work in Europe even though it is part of AT&T. I asked if it can text over wi-fi and was told no....it will be useless. Now from the USA I can get a plan to call almost anywhere in the world but can only make and get calls from inside the USA, (Canada and Mexico if I upgrade my plan).
Moral of story: If you do a lot of traveling check with a new carrier before you switch. In Europe I will have to rely on E-mail or buy a burner when I land to use for the week.