According to the source mentioned at the bottom of this post, the fine print on Airtel website states - "All Internet/data packs or plans (through which customer can avail discounted rate) shall only be valid for internet browsing and will exclude VoIP (Both incoming/ Outgoing). VoIP over data connectivity would be charged at standard data rates of 4p / 10 KB (3G service) and 10p / 10 KB (2G service)."\ With users opting for a number of VOIP apps like Viber, Nimbuzz, Skype etc, this might be the newest arena for revenue generation for Telecom operators. As is thanks to WhatApp and other IM (Instant Messaging) Clients, usage of SMS has dropped drastically. VOIP or Voice Over Internet has further reduced expenses made, especially when roaming. How this pans out, only time will tell. However I do see smaller operators coming out to counter this with no VOIP charge to try and lure customers. Taken from - airtel.in/Airtel3G/tariff.html And source - Airtel starts charging for VoIP data on 2G and 3G, calls on Viber and Skype not to be covered by data packs
And now they backtrack on it - Airtel backtracks on plans to charge you extra for VoIP calls -- for now - Hindustan Times