unlocked Iphone says Carrier: Not Available

Hello everyone! I bought 1 month ago an unlocked Iphone 5C from the apple store.

When I was looking in settings < general < About I saw that under Carrier it says Not Available instead of Carrier 13.0

I am very worried... Is my device unlocked? What happened? The only time I inserted a Sim Card, it was for setting it up. I inserted a Virgin Mobile SIM card

What can I do now? Please give me am answer because I am worried.