Hello Mr Amit
I got it.I will explain it what basic requirement it wud require.
1.Computer
2.Switch(Depend on seats)
3.Router(Depend on Seats)
4.VOIP Port(Depend Upon seat)
5.Lease LIne(For voice packet)-512 KBPS is ok for 20 to 24 seat.
6.Dialler
Dialler again two types.PD and Progressive.
Pd cost you from 25,000 to 1,00,000 for By out.
You can go with byout or on rent basis.
You can say mostly INR 1,00,000 to INR 1,20,000 would cost you per seat.
If you will go for monthly expense.That cost you $ 2.50 to $ 3.00 per seat per hour.
Now you can calculate by this way.
We also help organisation who want to setup call center.And provide them business.If you need and any help provide us your contact details.
Regards
Lalit Tyagi