what does this messge mean i have a black jack 2 with att.?

this phone can only be used with a specific sim. enter the unlock code or insert an apporoved sim.
what does this mean?
is it asking for a network control key or the pin for the phone it self.
i have att wireless.
do i have call att for this.
but if its asking me for the network control key and unlock it will be unlock for ever correct right.
 
Top