It's nothing to do with the cod's as they're already there in the 8900... they just can't be activated
It's all down to your carrier, and the device model they have logged on your account. As VVM is currently only available for the 9000 on AT&T, the only way you can get this working on an 8900 is by fooling them into thinking you have a 9000 on that account. I guess it's a compatible service book thing
I did read a post by a guy who had a friend at AT&T who changed his account device model from an 8900 to a 9000 and hey presto... VVM on his 8900