I got the sim the other day and had a text giving my new number and one saying that my serrings had been updated but my imessage isnt working how do i get it to work?
Connect to iTunes and let it update your settings, you do not need to do a sync. In iMessage is is showing both your phone number and email address correctly? Do you get the same error message if you try FaceTime?
In that case it will not work until activation is complete.
The activation message is sent to Apple servers and you have to wait for them to enable your iMessage. Usually it takes a few hours but sometimes much longer.