How is the new phone on my account not showing up on my account?

I recently upgraded phones on my second line, activated the phone and my son has been using it for Internet. He doesn't use it for texting or calls. But today he tried to and it said, "was emergency calls only". So it's clearly not activated. How is this and how has AT&T "activated" some services, but not all? His old phone is still showing up on my account as the one on the line.