Iphone 5 will not deliver text messages

I phone 5 will not send or receive text messages, red message pops up "Not Delivered". It will send and receive text messages only if a picture is attached. I have confirmed with my service provider that text messaging is included and part of the phone service. iMessage and FaceTime when turned on says "waiting for activation". Took the phone to Apple store the other day. After 3 hours they reset the phone several times, checked the software, and did who know what else only to tell me iMessage was down or being worked on and it should work in a little while. To ensure it was not a hardware issue I pressed Apple for a little insurance, they swaped the orgnal phone for a new phone. This did not fix the issue. Still no text message.