Thanks for posting in the community! Sorry to hear about the volume issues as this can certainly be frustrating! This is certainly strange as there shouldn't be a difference between controlling volume between apps on an iPhone as the volume should be controlling the master volume of the iPhone. Have you been able to test this with a different mobile device at all yet? I would also recommend trying to clear the pairing list by holding down the Bluetooth button down for about 10 seconds. A tone or voice prompt will emit stating the list is cleared. From here, you would want to forget the device on the iPhone and re-pair the speaker again.