Adjust The Volume On The Playback Device Connected Via Bluetooth; Adjust The Volume On The Sony | Headphones Connect App - Sony WF-1000XM3 Quick Start Manual

5. Check that the Left unit of the Change the touch sensor function is set to Volume
Control. You can now use the left unit touch sensor to adjust the headphones volume.

Adjust the volume on the playback device connected via Bluetooth

When making a call, you can adjust the volume as necessary on the playback device connected
via Bluetooth.

Adjust the volume on the Sony | Headphones Connect app

Install the Sony | Headphones Connect smartphone app, then change the volume using the
app.