If you are looking for domestic call center.
What is the Market you wanna catter to ?? As this will help in understanding from geographically which part of India your call center will be receiving calls to answer.
This way you first have to do a little homework in terms of finding the geographic location, distribution n number of calls from your target callers to your call center. Thus can have some kind of understanding in terms of the Volume of calls. Once you are through with this.
You can start designing the network for your callcenter. it terms how much call from which all cities you have to transfer to your centeral call center. To avoid paying STD rates on per call.
In the later stage you can short list out of different vendors who provide solutions on this.
few of them are
1) NORTEL – Principle System integrator – GTL Ltd.
2) Avaya – Principle System integrator – Tata Telecom