Stay away from Advanced VOIP billing, unless you like pain and suffering.
The support of the product is a pile of ***p,they do not even answer the phones during the Muslim holidays.
They claim that they have technicians on the US, but really answer the phones in Pakistan.
I use Data Techs Labs on my Quintum, with moderate loading and so far no mayor troubles.
Best luck!!!
Voicemaster???? Be sure that you talk with people that neededed support from them.
Wilson Boyrie.