Is a mobile company right in charging for VoIP?

Is a mobile company right in charging for VoIP?
One of the leading companies in India, Airtel announced that soon it will start charging for VoIP services on its mobile network. Its website under Mobile Prepaid service states A pack that gives you 100 MB of VoIP data at just Rs. 75 with 28 days validity. Surprising. First point that comes to mind is ...