Iphone 6 battery die in 3 hours

The iPhone 6 battery is totally suck, and the in store customer service is even worse.

This is what happening to my phone now, the battery runs from 100% to 0% within three hours without any app running, doing anything, or feeding in background.

My iphone 6 battery was totally fine until one IOS update, I couldn't recall which update it is, but I was 100% sure the battery works perfectly fine 5 months ago.

I used to take 500 pictures a day with my iphone, and it could still do it in October 2015. One day, after the IOS update, the phone battery drop extremely fast. I first brought in for Brea CA store repair without appointment. The Genius Bar tech run a diagnose and said to me that "the battery is 90% good, so as long as you close all the app in the background, it helps the battery so last longer."

I follow her instruction, however the battery still runs out fast, so I made an appoint with the Brea CA Genius Bar again within 1 weeks. The bar tech ran another diagnose again and told me the battery is 75% good. WOW, it drops 15% within a week!?!?

The reps shut down some background feeds or update, adjust some settings, and hand the phone back to me and told me it's ok now.

Was my phone fixed??? NOPE, the phone ran from 100% to shut down within 5 hours

I brought the phone in on 04/10/2016 to the Irvine Spectrum shop. The tech ran another diagnose for me and told me the phone battery is 50% good. WOW, drop another 25%??

He told me there no need to replace the battery until it's only 20% good.

The tech also said the IOS is corrupted, so he gonna recode/ reinstall the app. It took 2 hours to completely install the IOS and reinstate all the back up.

Is the problem fixed???/ NO, my phone battery drops from 100% to 0% within three hours now, and my desktop and car charger can longer charge my phone, it only stop the battery from going down.

I really think you guys intentionally not to fix my phone and let the battery die, so I need to spend money to replace the battery.