i have a chrysler concorde 1999 and just got it from a dealer but recently i had a problem with the battery.?

[Makanga]

when i took it to the dealer they said the alternator and battery were bad . i told them to replace them and almost 800$ on that. the problem was not fixed though , the alternator was not charging the battery. they tried checking for bad wires but there was nothing they also tried changing the computer but nothing happened. my interior lights also stay until the drain the battery out anyone has a solution