iMessage on unlocked iPhone 4

[vonWachtstain]

My father in law has unlocked iPhone 4. Last night he wanted me to show him how to use iMesssage but when I tried to set it up it only stays for long time on "waiting for activation." Is it possible that its doing this because he put text block with Tmobile? Or is there something else I am overlooking?

 

[Vell843]

Is FaceTime turned on? If not, I have heard that that does the trick?