Why does my screen say "Unknown" at the top left corner?

[baileytoo]

I thought I set up all my preferences, but the screen saver says "Unknown" at the top left corner and I can't get rid of it or figure out why? Anyone know?
10/29/15 - I figured it out, it is supposed to say the name of my carrier, I just rebooted it and it fixed itself.

 

[sethyboy]

What phone is this? Do you have a SIM card inside the phone? I think it should usually display your carrier name in that area (like "Verizon Wireless", "AT&T", etc.)