Hey all. My family has 3 of these phones and all 3 have very low volume in both the earpiece and speakerphone on voice calls. You can fix this by disabling Enhanced 4G LTE Mode for phone calls. Once you do that the little VoLTE icon should no longer be present when you pull down the notification shade. Calls are really loud and clear with this setting off so I'm not sure if there is some bug here or not. Not all carriers support this feature so YMMV. We're on Straight Talk in the US on a TMobile SIM.