Why is my Iphone 5c not getting 3g but it can connect to Wi-Fi?

I woke up this morning and was texting my friend fine with 3g imessages. I then put my phone down to charge and went to eat. I came back about a half hour later and I could not imessage my friend. It said my messages were not sending. Also usually our conversations are in blue, but now they are in green and not sending. Any ideas what to do? I restarted my phone and that didn't help, I can only text while connected to Wi-Fi.

Have you tried going outside? My daughter has an iPhone 5 and doesn't get any cellular service in the house.

For the record, the blue messages are iMessages; green are text messages.

As far as what to do, if it persists contact your carrier about it.