Can I change the Wi-Fi password with my iPhone?

Check the route settings -> Recommended settings for Wi-Fi routers and access points

Recommended settings for Wi-Fi routers and access points - Apple Support

If you need help with your Wi‑Fi password

If you need help with your Wi‑Fi password – Apple Support (UK)

•  You need to sign in to your router.
• The Wi-Fi network name, or SSID (service set identifier), is the name your network that has a password.

or If you have iOS 16 / iPadOS 16:

Go to -> Settings -> tap Wi-Fi -> tap on the hideen Password -> enter Passcode -> you will then see the Wi-Fi Password.

WiFi is through your internet provider, so to change the password you have to go to your internet provider's website to change the password.

Good Luck!

If you mean you want to change the password to your iPhone's Personal Hotspot, go to Settings>Personal Hotspot>WiFi Password and tap to edit.