Keywords: no volume, low volume, volume, apple maps, siri, direction, adjust volume
The volume can only be adjusted when it's playing ( in a call or broadcasting GPS) E.g. only in the short period when it's broadcasting the navigation. When it suspends broadcasting before next broadcasting, you turn the knob, the volume will have no change.
But the ringtone volume may not be adjusted. It depends on phones. If the ringtone volume is too low, please contact firstname.lastname@example.org. We’ll replace for you. We have turned up the standard volume in the later batch.