I was having problems using the voice command feature due to the format of the iphone's address book.
The unit requires the format of 1112223333 for stored phone numbers.
The iphone's default is (111) 222-3333, which will not work.
The easiest way I came up with to solve the problem is as such.
If you have already transferred your phone book to the unit, the steps are as follows:
1) Clear the phone book that is currently on the F series unit.
2) On your iphone (3g is what I'm using so this was my reference), go to settings --> general --> scroll down to international --> then click on region format --> and choose australia.
This removes the brackets and the dashes. (Also, of course, make sure the contact names do not have any symbols in them, i.e. & . , etc.)
3) Connect your iphone to your F series unit via bluetooth and transfer your phone book data over.
4) Done!! Voice command should work perfectly. You can change your iphone's region back to US or Canada or you can leave it as Australia to assist in getting the proper information to display on your unit when some one calls.