Open the WhatsApp app on your phone, and tap the three dots symbol that appears on the upper right corner of the screen.
Then choose “Payments”.
The next step is to choose the bank account whose UPI PIN you have forgotten.
Then, under the option "Forgot UPI PIN", select "Continue."
Then, input your debit card number's last six digits & the expiration date.
certain banks may ask you to submit your card's CVV number.
After that, input the OTP and the desired new UPI PIN.
Finally, confirm your new UPI PIN, and you're all set to go.