Not sure if it has anything to do with the recent IOS upgrade or not but I noticed today that the volume of the caller on my iPhone 6 is very low. Even using the side volume up/down button's won't increase it enough. Speaker volume and music volume all seem to be normal but when listening to callers, I can barely hear them even a full volume. Is there any type of master volume control in settings (can't find one) that would enable me to increase this volume? I tried a reset of the setting but nothing changed. Any help would be appreciated. Thanks