iPhone 15 Pro I keep inadvertently switching off the ringer

Since you seem prone to tapping the action button inadvertently, turn the action button off and this won't happen.

Go to Settings > Action Button > and slide through the options until you land on none then close the settings app and the Action Button will no longer mute your phone. In the future to mute your phone, you'll just pull down from the upper right hand corner of your iPhone to open Control Center, where you can mute the phone there if you need to mute it.