Why does the Iphone 13 volume constantly change?

I have the sound buttons turned off in "Sounds & Haptics", however my volume changes for every app I open. If I am playing music on Spotify at a low volume and switch to a different app my volume is suddenly turned up all the way. If I turn my volume down, close an app and then reopen it, it also turns all the way up. Is there a way to lock the volume setting to never go above a certain level? My phone is constantly blaring sound, even right after I turn the sound down. This is ridiculously annoying.