Interconnect restriction can be used for this as well, I set it up a few weeks ago for a hotel customer. House phones are in Interconnect 1, guest room phones in Interconnect 2, and voice mail ports are in Interconnect 3. Interconnect 3 is restricted from 2, and in addition, we have the VM ports in Intercept Group 3 and have that Intercept set up so that any interconnect violations are sent to the front desk.