HDFC Bank — non receipt of otp

This is my second complaint after I did not receive any reply from HDFC since I posted the same complaint two months ago.

I have not been receiving any OTPs on my registered mobile number for the last 5 months now.
This is after I updated my new mobile number by the two suggested methods i.e in the bank branch and through my online net banking account as well.
I have spoken to customer service over the phone, I have been to my local branch and raised the issue numerous times and I have also written emails to [protected]@hdfc.com for last 5 months now and no one has made a real effort to solve the issue.
I have mentioned so many times to every supporting department that I do get SMS alerts on my registered mobile number but I do not receive any OTPs for any online or net banking transactions.
Its really frustrating and exhausting that after so many months, no one has still been able to resolve this issue for me.