What is causing my battery to die? Not the alternator, had it tested.

What is your question?

I've only had this Kia since April and the battery had gone dead twice. Had it recharged, it's a good battery. Then had the alternator checked and it tested good, no problem. What else could be causing the battery to die? I do not keep anything plugged in such a my phone charger, I turn off the radio and fan before I shut off the car. Any suggestions before I pay too much for a service check?