Block traffic from and to vonage?

[akoei]

I can block traffic initialed by Vonage from WAN rule, but if some traffic initialed from my LAN, it will pass the fw and Vonage can do provision my VOIP. How to block any traffic from/to vonage no matter it initialed by any end?

[cmb]

Block their networks in firewall rules. It might be hard to determine what all their networks are though.