Same for me, I get around 5.5- 6 hrs of screen time for 80-85% battery use but am able to get approx 7.5hrs of screen time on full charge. I also run a lot of routines in the background, keep my Bluetooth and location on 24hrs (for routines) along with highest resolution in settings. I think if I optimize these settings a bit 9-10hrs on a full charge probably seems doable. Check these settings for your phone, might be helpful to increase the battery life before taking the phone to service centre.