HDFC Bank review: not getting otp on my registered number with hdfc bank account

I did the shopping on amazon.com and I needed "One Time Password" to buy the products but HDFC bank did not send me "One Time Password" and I was unable to buy products. I tried many times to click on the button "resend" but no "OTP" was gotten on my registered mobile number and I could not buy my products from amazon. Please start the service of "OTP" on my number. I want "OTP" on my number so that I can again buy products from amazon. Please do this fast. I will be very thankful.
My contact number is +[protected]