How to find out what carrier this iphone 4s belongs to?

I found an iphone 42 16gb in my house. We have parties to say the least (college). Anyway, the phone has a password and I can't get into it. Even if I could, how would I be able to tell the carrier?

Try using a password cracking software unless you can't find the right owner of the mobile. Best thing is try to find the owner and give it back as a gentleman.http://www.iphone5casestore.com/

Press the power button and see what it says on the upper-left corner. The carrier name will show there usually.

It's in the corner of the screen dude