1. This product only supports volume adjustment via the Roller.
2. Due to compatibility differences in Bluetooth protocol versions across operating systems, some phones or computers may not support the volume control protocol. This is a known limitation affecting many over-ear Bluetooth headphones on the market.
If you encounter this issue, try connecting the headphones to another commonly used device and try to adjust the volume. If volume control works as expected on the other device, the issue lies with your device, not the headphones.