as far as I know that is the latest official firmware that should have the low volume fix. I'm away from my computer at the moment so I can't check, but some other threads on this forum should be able to tell you more.
hope you get it sorted.
edit: when you tried to update the phone did you follow this procedure:
1. Go to "Settings"
2. Press "About Phone"
3. Tap "Online Upgrade"
4. Tap "Firmware upgrade"
5. Your phone will check for an upgrade and will show a new version name: "Asura_Vodafone_B885"
6. Press Download - you will be reminded to connect to WiFi
7. Press OK and the download will commence
8. Your phone will restart to install firmware after finishing download
If you did and there is no update then the low volume fix should be already in place. If it were me, even though it is hassle I would take it into a vodafone store and explain your issue. They will probably fiddle with it and either offer you a replacement or get a refund.
Also worth mentioning is have you rebooted your phone since you first switched it on? As daft as it sounds it can make a difference.
all the best.
Edited by runlevel5, 20 June 2012 - 05:22 PM.