How to tell if galaxy s7 is a new phone

[Android Central Question]

I bought galaxy s7 new at boost store in April. I have issues one after the other. When I factory reset it it said file not found and something with Att it did reset but now I think it may not be new was it rooted from att is there any way to tell?

 

[Rukbat]

AT&T doesn't root phones. Was it used? There's no way to tell now, after a reset.