New iPhone5 cannot send/receive text messages

I ordered a new iphone5 for my wife, I already had an iphone4. Her phone arrived and she was trying it out. It cannot send text messages to my phone and cannot receive text messages from my phone.

I searched the internet and found suggestions to make sure the settings had the right phone number, had various messaging things turned on, etc. Every setting in her phone was set the way it was supposed to be, I didn't find anything that seemed to need changing. She can make phonecalls to my phone, just can't send text messages.