Most drug dealers or johns I see just buy a prepaid phone from Walgreens, i.e. a booty phone. Tracfone doesn't verify whatever you activate with, you can just make up whatever name/address.
That's not really a secure phone or black phone, that's just a prepaid phone. Nothing inherently secure about it other than it's difficult to trace. The parent was talking about purposefully secured phones with encrypted phone call and messaging, etc.