Seems like the volume control button on my bluetooth headset is broken, is there any way to change the bluetooth volume directly on the phone? I am on Android 4.1.2, just in case it's relevant. I found settings to change the normal front speaker volume, but nothing for the bluetooth volume.
See if this helps. I am not sure though:
Settings >> Sound >> Volumes
If this doesn't help try this Bluetooth Volume app. This should do it.
And you are on Android 4.2?! WHAT??! AFAIK as of now 4.1 Jelly Bean is the latest... And 4.2 was supposed to launch in tomorrow's Google event. (The event is apparently cancelled) How come you are already on 4.2?
No way change your Bluetooth device or repair because volume up down is separated you can adjust phone volume or Bluetooth headset volume. When Bluetooth device volume is zero then phone volume increase you can't hear.