How to adjust the volume of the conversation ?

You have two ways to adjust the volume of the conversation.
The first is to use the + and – buttons of the Bluetooth kit by making long presses (about 2 secs).
The second solution is to do it on your phone once the kit is connected. Usually you can adjust the volume with a button on the side of your phone. These two ways adjust the same volume (Bluetooth volume of the phone).