Why won't my at&t prepaid sim card work in my unlocked blackberry bold?

I purchased a prepaid sim card and it will not work in my blackberry bold. Does anybody have a reason for this?Why won't my at%26amp;t prepaid sim card work in my unlocked blackberry bold?
AT%26amp;T prepaid service is not compatible for blackberry's.Why won't my at%26amp;t prepaid sim card work in my unlocked blackberry bold?
hello

SIm card not activated or not registered or may be your blackberry is locked.

you can get unlock code by calling your network service provider its take 2-20 hour or you can get the unlock code by the third party its take 2-12 hours

this website will help you a lotWhy won't my at%26amp;t prepaid sim card work in my unlocked blackberry bold?
Has the sim card been registered? Any sim card from AT%26amp;T that is activated and registered shoul fit in a phone with a sim slot.