What's your phone’s firmware version (Settings> About phone> Build number)
Are you talking about battery drains in standby mode or in use?
If you think that there’s battery draining in standby mode, please charge your phone to full before going to sleep, and leave it unused and unplugged overnight. Please capture 2 screenshots as below on the next morning before you use your phone and tell me how many percentage of power the phone has consumed overnight:
1. Battery : settings> Battery
2. History details: settings> Battery> please click the sheet
Sorry for any inconvenience.