I m unable to update ios 15 . It’s showing connect to wifi though my iPhone is connected to wifi and phone connected to charger

If you’re not connected to a hotspot, and not running a n add-on VPN, try restarting the iPhone.

If you are connected to a hotspot, connect to a MiFi or wired-back-haul Wi-Fi.

If using an add-on VPN app, remove the VPN and restart and retry.

Hello ~ What happens when you try? Messages/errors? Are you using a VPN? Are you connected to WiFi? In the meantime take a look here and post back with info :

Update your iPhone, iPad, or iPod touch

~Katana-San~

Hello ~ Can you tell us what is your current iPhone model and iOS. Also do you have enough device storage?

How to check the storage on your iPhone, iPad, and iPod touch

~Katana-San~

iPhone 12 Pro Max

128g

2 tb in iCloud

In addition to the above checks, make sure you’re not in low-power mode.