Yep, sorry to hear of your troubles. I am having the same problem as well. One day a few weeks ago my phone unexpectedly died - thought I forgot to charge it. Charged it fully but found it was dead at the end of the day. Happened the third day and the fourth. I've just made 5 visits with my phone to two Apple stores in the past few weeks with no success.
First, they wiped out the phone and re-installed everything after running diagnostics and not finding anything. Didn't help, the phone continued to die in less than a day. This is with zero notifications, all background refresh off and low power mode - as I always have it set. I also do not have a single song or video on the phone and the only game is solitaire... I only make 1 or 2 calls a day and send less than 10 texts a day - if any at all.
Took it back to Apple, the tech said I need to replace the battery - even though the second diagnostic test showed no issues. Looks like I threw $90 out the window replacing a battery that wasn't the cause of the problem.
Screen shot shows that I charged the battery to 100% at 10:24 PM that night. Unplugged it. In the morning I checked the phone at 5:58 AM and the phone with one-day-old battery had lost 50% of it's charge just sitting on the counter overnight.
Took it back to Apple. Showed them screen shot for reference. They ran tests, saw "nothing". They reset the phone. Again.
Same thing, the brand-new battery continued to drain in just a matter of hours even when all notifications and background refresh are off and, I would make, maybe one call or send one text. Went back to Apple, techs can't see anything wrong with my phone according to their diagnostics.
Here you see, I fully charged the phone, at 6:50 PM. Didn't touch it all night. Picked it up at 6:18 AM and the brand new battery had only 10% TEN PERCENT of its charge remaining.
Went back to Apple store a-g-a-i-n. Showed them screenshots. Test run. Nothing. According to the five Apple technicians I saw, there is nothing wrong with my phone. They implied its that I don't know how to use my phone properly or understand appropriate settings. The only suggestion I was given was to buy a new phone if I don't like the fact that my phone's brand new battery dies after only hours of charging it.
During every visit I asked each tech, 'Is there some app or virus that is damaging iPhones? Have you gotten anyone else coming in with the same issue?' Repeatedly, I was told. No.
Something - Is - Definitely - WRONG - With - My - iPhone! And.... I AM NOT GETTING THE LEVEL I EXPECT FROM APPLE.
Having been a faithful Apple user for 20 years I am disgusted but the complete lack of care or attention. Apple was not able to diagnose the problem with my phone or make any repair so, they've dismissed me.
Apple products cost many more times the price that Androids and PCs cost. I was literally researching what new model Macbook Pro to replace my 4-year old one with when this all came up. Between to ridiculous new ports on laptops requiring me to replace every peripheral I have and being completely abandoned with my phone that only lasts a few hours, I am very seriously considering making the jump and switching to PC and Android (which I use at work so I'm completely vers in both platforms). I'll save a few thousand dollars at the very least.