Hello,
Thanks for this useful information. I was not aware about so much about this call flow. Exactly I did'nt know about operational flow like call charges etc. I have experience in technical side like how routing done, what are the interface between two entities etc. Any way thanks for your reply.

Now my next query is as follow.

In these days some companies (like spice mobiles ) are launching phone with dual technology (GSM + CDMA). Sincd GSM and CDMA are different technology , how a phone support dual sim feature?

Thanks in advance
Gaurav Bhatnagar