To hit Contacts and its subfolders...
Sub FixFileAs()
Dim ns As NameSpace
Dim mf As MAPIFolder
Set ns = Application.GetNamespace("MAPI")
Set mf = ns.GetDefaultFolder(olFolderContacts)
ActuallyDoIt mf
For Each mf In ns.GetDefaultFolder(olFolderContacts).Folders
ActuallyDoIt mf
Next
Set mf = Nothing
Set ns = Nothing
MsgBox "Done"
End Sub
Private Sub ActuallyDoIt(ByRef mf As MAPIFolder)
Dim ctact As ContactItem
Dim it As Object
For Each it In mf.Items
If it.Class = olContact Then
Set ctact = it
With ctact
.FileAs = .LastName & ", " & .FirstName
.Save
End With
End If
Next
Set it = Nothing
Set ctact = Nothing
End Sub