Hmmmmm
lot of fuss and descussions abt Voip
Its real easy
what u need is
2 P4 both 512 ram
10 to 20 client
p3 800Mhz 256mb ram
Rest is upto u go for
CISCO CCM
Five 9
Asterisk (I prefer this)
U need a skilled person lik me and walla i can do the job at lowest cost and what ever bandwidth u have complete with Predictive Dialer