You can't buy Bitcoin in India for now as it was possible earlier till the January 2018. But, you can use the third party to buy Bitcoin in India. As, you know already that the most trustable exchange Zebpay facilitate the buying and selling of the Bitcoin in India but now it has stopped it's service for India after the banning of Banking service by RBI last year. Also, all other exchanges was affected by this step by RBI. But, now only one is working efficiently that is UNOCOIN. You can buy Bitcoin from here with the help of third party website AirTm.
If you know Unocoin and Zebpay then you must probably know WazirX too since Zebpay was a rival to WazirX.
Just when India passed strict rules to banks to freeze the accounts of crypto users, Zebpay decided to stop it's exchange from functioning in India.
WazirX took the lead and decided to launch a peer to peer exchange and has successfully establishes itself over the time.
I would recommend every Indian user to use WazirX peer to peer exchange to buy and sell crypto. It's hassle free and easy to use.