Whatsapp started the payment feature in india which is roling to the customers in the phased manner. first of all it goes to the beta users then after first phase it will go further.
Now if you dont get the payment option in your whatsapp till now then their is a trick to get it fast.
for this you have to get invite from the user how have that feature already installed but you must have updated version of the whatsapp.
For whatsapp invite
whatsapp me on my no. 9463697173
i will send you payment invite.