iPhone 7's battery draining

Dear Apple,

I am writing this because I am feeling disappointed. My hopes were painfully wasted.

However, I bought an iPhone 7 with a 128 GBs of storage a couple weeks ago. It felt perfect to hold such a unique and accurate phone. It works perfectly but when I tend to describe its battery you would get surprised. Before the last update, I have noticed that the battery is draining fastly on my phone. After the update, I activated " Don't disturb me " mode, as well as " flight mode " and " low power mode " and slept. the battery was at 97%. I set 3 or 4 alarms and slept for about 7 hours. The battery was when i wake up at 85% and imagine my feeling.

I am so disappointed. Steve would have been very disappointed too about this problem. Please Apple, give me a solution.