This question is often asked more times than I can count. First of all, unblocking the cellular bands and any restrictive bands for that matter is illegal. Assuming the BCD 396-XT can be unblocked, you will not hear any cellular callers, as analog cellphone service shifted to encrypted digital signals. Digital scanners cannot decrypt encrypted digital signals anyways, so what your asking to be done is pointless, and against the law.
If you absolutely wish to break the law, and assuming your device is capable of such modifications, I suggest doing some research, as there is a plethora of information to be found. Just remember, there is nothing you will be able to receive assuming your device is modifiable, and of course breaking the law is on your hands, and yours alone.