What Service Do I Have?

It's a few ways to check the carrier you currently have. One way is to go into settings and click cellular. Once you enter cellular right underneath personal hotspot you will see your carrier name. (Ex: Verizon) 

Another way to find out what carrier you have is swiping down from the upper left hand corner or the upper right hand corner. When you swipe down you will see your carrier name there usually next to the Wifi symbol.