Unfixable battery drain

My Samsung Galaxy S5 has had an awful battery ever since the Lollipop update. The battery drainer seems to be "Android System" under the battery stats. I did the usual battery saving techniques, didn't work, factory reset the phone about literally 15 times. It's pretty sad when a daily factory reset is normal... When I tap on android system it seems to be keeping my phone awake under the "Stay Awake" bar, the bar is on a lot of the time. The Stay Awake time of AS is about 45min at the end of the day (on batt for 15 hrs), which is ridiculous. I've done everything that AT&T and samsung told me to do, but to no avail have I had any luck getting it fixed. I even out it into safe mode to see if it was continung to count up to see if it was a app off the play store. To my surprise it STILL was counting up, I didn't know what the heck to do then. Oh, and when I factory reset it the stay awake time seems to be about 4min at the end of the day for that day ONLY. The next morning when I unplug it, and about an hour later there's android system keeping it awake for already 15min and it's only say 95%... I've done literally everything I can do. I went to a Samsung Experience shop, the person told me this, and I quote, I've never seen this before, I don't know how to fix it, contact AT&T." Both companies just throw me back and forth, and back and forth. I'm ready to say the h*ll with it and go back to iOS where I NEVER had a battery drain issue. I just love worring about carring a wall, AND car charger in my pocket so my phone will last me... I'm ready to go get my car and run over my phone with it, and get an iphone. I switched from an iphone 5 to a GS5 and before this issue I loved the GS5, I prefered it way above an iphone, but now, it's the COMPLETE OPPOSITE!