A temporary solution until you get it fixed is to put in a battery cutoff switch
at the negative ground terminal. That is also useful for when you are working
on the car and the first instruction is: "Disconnect the battery ground". lol

Cut it off when you park the car. If the battery still loses charge, you have a
battery problem. A New battery is no guarantee that it is a good new battery.

The testers at the a-parts store will detect a surface charge that tells them
the battery is good.....but if it drains when disconnected, take it back.
Request another battery with authority.
Most places will swap out a bad battery once.