Help Samsung Galaxy S3 wont connect to Network

[chcospice]

I have a almost brand new Samsung Galaxy
woke up this morning and getting a message not registerd to network
i took it in and they used my sim in another phone and it worked
they said its the phone
i tried factory default as well
any suggestions to fix this is appreciated

 

[Rukbat]

"Almost brand new" means "under warranty". Why didn't they replace the phone?

 

[jmatherly411]

When you say "almost brand new" has it been used by someone else before you purchased it, did it work before?

If someone had it before you it sounds like the phone has been blacklisted, reported as stolen, or whoever had it before you had a unpaid bill.