OTP and PIN are secret

"Sir, I am calling from your bank. I sent an OTP to stop your card from being blocked. Please tell me the OTP quickly."

Answer: Scam. Bank staff never ask for an OTP. Once you tell it, the thief takes your money.

You just opened your own bank app to log in. This SMS arrives:

482913 is your OTP to log in. Do NOT share it with anyone. - HDFC Bank

Answer: Safe. You asked for this OTP yourself, so it is safe. Type it only into your own app and never tell it to anyone.