I have an a930 with VWZ service that I have fooled around with to get BT DUN to work. You have to enable BT in two different spots to get the DUN option.
1st spot...
->Menu
-->Settings
--->Phone Settings
---->PC Connection
----->Bluetooth
2nd spot...
->Menu
-->Settings
--->Bluetooth
---->Settings
----->Discovery Mode
------>On
I hope this works for you. :approve:
Check out
MyPDA under useful guides and go the the Bluetooth Guide. I has been a help to me in the past.