Why my phone say emergency calls only?

Hey there!
The "emergency calls only" could be caused by a disabled/missing SIM card, an active carrier lock, poor signal, or an unpaid bill.
Check if you have a SIM card in your phone. If you don't then that's the cause of the problem.
If you have a SIM card you could try restarting your phone, making sure the card is properly seated, and checking if your service provider doesn't have an outage.

Hope this helps (: