It occurred to me this morning that KC's claim to owning a BlackJack might be as simple as this: She had stolen $$ (from her grandparents?) by using a routing/account number from an old check to pay AT&T. The amount, IIRC, was around $300-400. That's the same rough amount a BlackJack from AT&T costs if you aren't signing up for a new plan. I'm thinking someone had already given her $ to pay that bill (Cindy?) and KC needed to come up with a reason why AT&T needed more money...so, KC comes up with the BlackJack story. I don't doubt that she knew how much they cost because I can see her trying to figure out a way to get one for herself. She filed that information away until she was caught out for stealing from her grandparents. I bet Cindy had given KC cash to pay that AT&T bill and KC spent it....then KC had to think quickly to come up with a reason why AT&T would need more $$ so soon.
Anyway, I don't have any proof of this theory other than KC is a liar and she did steal money (in a similar amount as the cost of a BlackJack) that went to AT&T. I imagine her griping about it not working/holding a charge was her excuse when CA saw KC using the "old" phone after having been told KC had a BlackJack. I imagine that KC told lots of lies about where the money that CA/GA KNOWINGLY gave her went.
JMO!!
PS: my son does have a BlackJack (first thing he bought after getting his first job at age 17) and has never complained about a charging issue. He doesn't talk on it much, but has texts in the thousands every month....HE was smart enough to get an unlimited texting plan! LOL