Please

[Genesmom1997]

Phones stays on emergency calls only

 

[mhinc]

Phones stays on emergency calls only

It's most likely your SIM card causing the issue. Have you tried simply shutting down your phone and turning it back on? Try taking out your SIM and putting it back in, then turning back on.
Are you getting a circle with a line through a symbol at the top instead of bars?

 

[acejavelin]

Phones stays on emergency calls only

This can be caused by a couple of reasons, the most common is poor signal for your carrier and no roaming is enabled or the carrier your phone can connect to is not a roaming partner with your carrier... but by law in most countries emergency calls must be allowed from any device connected to the network. The second most common reason is as mhinc stated, there is a problem with the phone reading the SIM card or the SIM card is defective.

Some other possibilities off the top of my head are your carrier has turned off your service (for non-payment, as an example), your prepaid plan has expired or not renewed properly, or the IMEI of your device has been black listed or reported stolen. There are other reason, but they are much less likely than even these...