Why does my iPhone 6S Plus not have service?

I just got the new iPhone and it came with a verizon SIM card in it already. I then switched it with my Metro PCS SIM card and it was working. Then I left it on my desk and when I woke up the next morning, i had no service. I reset the network settings and restarted my phone. Can someone help me please.

I'm surprised that your service provider couldn't solve this issue for you.

If you haven't bothered asking them yet, I'd also be surprised at that.