I'm pretty sure there are some 3rd party apps that will let you do that without the physical buttons.
In iPhones, there's even a built-in tool for doing things like that.
From a quick research I just found that it's called
Assistive touch.
I don't know if that is the result of accidental damage or something else, but there's no harm in resetting app preferences, clearing cache and restarting the phone.
This may or may not work but it actually fixed the Bluetooth not working problem on my phone after update.