Customers place a call to the toll free number
The call reaches the PSTN (Public Switched Telephony Network)
Depending on the routing opted for by the company, the call is sent via satellite (satellite telephony) or via the Internet (VoIP)
The call reaches the Indian PSTN
This is where it gets a little complicated:
The call is received by an IVR (Interactive Voice Response) System, and an Automated Call Distributor (ACD) is used to send the call to a Customer Service Executive (CSE) in the right department-based on the options selected from the IVR.