Why do you want to block the VOIP traffic? If you are experiencing issues, I recommend you configure the pipes for traffic shaping, and reserve specific minimum slices for network management, data, and voice/video. Traffic shaping will prevent a particular service (such as voip or ftp) from clogging the pipes. I recommend taking this up with your WAN engineers (including the service providers). I do not recommend blocking all VOIP packets across the pipe unless you have a WAN pipe specifically dedicated to VOIP traffic, in which case you should get your WAN engineers to fix the routing appropriately.
Woody Fairley CCNA, MCITP, CCP, JNCIA-JUNOS, CISSP
PS - technologies such as VTP provide mechanisms for traffic management at layer 2, and I recommend getting your network admins involved, or attend some training classes. As a minimum, I recommend Juniper Networks' free online training program which may help clarify some confusion regarding VLANS, VOIP, WAN pipes, carriers, and QoS.