If the orange dot says Accessibility, something in Settings > Accessibility is still listening.
Turn these off if they're on: Voice Control, Sound Recognition, Live Captions, and Switch Control. Then open Control Center and make sure Live Listen (the ear icon) is off.
Also check Settings > Accessibility > Accessibility Shortcut. If Voice Control is on that shortcut, a triple-click of the side button turns the mic back on. Remove it.
Lock the phone for a few seconds and the dot should drop. Settings > Privacy & Security > Microphone shows any normal apps that can still use it.