2 phones and 2 carriers.
The company I work for has many offices in remote locations. These are remote shorelines of the United States and sometimes on the offshore oil rigs in the Gulf of Mexico.
We use Andriod phones on AT&T network for those that need to talk and surf the net at the same time and iPhones on Verizon network for those that just want a phone that works most anywhere.
I work out of an office in Everett, WA, and go near Canada a lot, and this causes roaming issues at times for both networks. However, in places like Neah Bay, WA, or Hilo, Hawaii, having a phone that actually can make and take calls comes in very handy. This is why I carry an iPhone 5S on the Verizon network.
Me and three others in the shop were the last to get smart phones since we waited for Verizon to pick up the iPhone first.
The only places I have ever seen another network work better was Treasure Island, CA. Nextel had better service at that location, but that was also a few years ago.
On a side note, some of our vessels have Globalstar handheld phones that can actually be a satellite phone and a cell phone on the Verizon network. You get a satellite phone number and service from one provider and if wanted, activate it as a cell phone through Verizon as well. I keep one of these in my car for when I go hiking and can be reached on cellular or satellite if need be.