You can easily adjust the in-call volume during an active voice call. You will see a large red icon with a phone with two other buttons on the screen: a plus (+) icon and a minus (-) icon. Repeatedly tap the plus icon and you will notice the row of dots below move from left to right to indicate lower and higher volumes. If the dots do not move, this will indicate the volume is at maximum level and vice versa for lowering the volume. For further assistance, please contact our Support Team here.