pls suggest internet calling app without Latency

Latency primarily depends on your internet connection.

Try google duo, signal. If you are using a crappy phone these issues occur. Because these apps needs to encrypt these and process, if your phone is slow you might experience this.

Try " Google Hangouts". it is the best calling application in India. Atleast it is better than whatsapp in terms of latency and sound quality.

Don’t use WhatsApp, lag will be there. Try signal, I’m using it daily for voice and it is as good as normal network call.

Try Skype, better than anyone.

Change your net connection instead.
Whatspp n duo both have best latency round the world.
Coz once the call is established mostly voice travel p2p.
Latency of 2-4sec is too much. You wont note the delay if round trio latncy is less than 1/2 sec.