Telecom major Bharti Airtel here on Monday announced expansion of Voice over Wi-Fi service, "Airtel Wi-Fi Calling" to Mumbai, Kolkata, Andhra Pradesh, Karnataka and Tamil Nadu.

The service was launched in the national capital earlier this month.

'Airtel Wi-Fi Calling' uses Wi-Fi networks to create a dedicated channel for voice calls and allows customers to make telco grade calls to any network. It improves customer experience as one can seamlessly switch to Airtel Wi-Fi Calling, according to an Airtel statement, here.

There is no extra charge for calls made over 'Airtel Wi-Fi Calling' and the application consumes minimal data, it said adding the service didn't require any app and could be configured on smartphone.

Airtel is working with all leading smartphone brands for compatibility with the service. It is currently compatible with Airtel Xstream Fiber home broadband and will soon be compatible with all broadband services and Wi-Fi hotspots.