TS2755: iOS: Troubleshooting MessagesLearn about iOS: Troubleshooting Messages
Currently Being ModeratedMar 2, 2013 8:48 PM (in response to nanookgirl)
Try to unsign and sign in again.
For FaceTime and iMessage chosse to use your email address instead of your mobile number.
Go to Settings>>Message>>Send&Receive and set your email address.
If it is still not working, unsign your Apple ID and select your mobile number ("+" "country code" "mobile number").
Also check in: Settings>>Message if you turned on iMessage before. Here, turn off "Show Subject Field".
Change your address for your currently location. If not works, change it for your native country.
Did you turn on iCloud as well?
Hope this help