If you found you cannot control volume via button “+” “-” on headset, you may check below pls:
1) The volume control button "+" "-" only works in Bluetooth mode NOT wired mode.
2) Make sure your CLIP/TAP the "+" "-" but NOT press and hold it.
3) Use HT3189 on your smart phone/tablet, check if you can adjust the volume.
4) ONLY pair the AS9S headphones with your smart phone, check if you can adjust the volume.
If all above failed, then contact firstname.lastname@example.org with your order number for FREE replacement pls.
If any more help needed, you may contact email@example.com for help. Also, to make sure all our users can use Avantree products properly, we offer Avantree Online Clinic to help you with your set up / installation FREE of Charge, click below link for details: