Why does my nexus 5 never have a signal?

A

AC Question

I have tried everything it says it has lte until I try to make a call then I have no signal at all. I have t mobile and I bought the phone from Google. I returned it once already for the same issue. It doesn't have WiFi calling so I seldom as actually get my calls it just pops up with a voice mail. I even have Google WiFi in my house and still no cell service.