Here's a tip, though, if you ever get concerned about whether or not a phone will work with your carrier. Check what modem it has. In the PinePhone's case, it's the EG25-G.
http://files.pine64.org/doc/datasheet/project_anakin/LTE_mod...
So now that we know the name, let's look and see if your carrier mentions it as one it approves. For the sake of brevity, I'll assume you're on AT&T.
https://www.att.com/modules
Google's cache nicely and conveniently converts spreadsheets into web documents, so let's view it on that:
https://webcache.googleusercontent.com/search?q=cache:G7My6z...
The EG25-G is #51, and is fully supported.