iphone 6s battery draining too fast

Good day Apple!

I upgraded my IOS to IOS 11.3. After the update, my phone drains too fast even just after charging. Even if i have not used my phone. I tried those hard resets and erased all the settings and other things that eat up too much battery. Now, i would like to inquire, how this battery issue will be solved by Apple? lots of problems have been raised already regarding the battery...! How i wish, we will be assisted! Thank you