Question

Is Airtel unlimited call and 1 gb per day data plan available only for 4g handset user or it works with 3g handset also?

Answer 1

No, the airtel 4G service is only available with $G handset and not only airtel but all the  telecom companies in India provide 4G service with only $G handset. This is because of there connectivity issue with 3G handsets.

Answer 2

It is not available but by downloading some network converter apps or dialing a USSD code, anyone can use 4g sim in 3g handsets. But this may damage your device if not operated properly.