HDFC Bank — Pre approved millennia credit card application rejection

Around one month ago i got a call from hdfc bank representative stating that i have an offer for pre approved millennia credit card. Then i visited my hdfc branch ( my hdfc account branch) where they confirmed that i have an offer for pre approved lifetime free millennia credit card with no conditions whatsoever like spending conditions etc. Then i applied for the same at my home hdfc branch through offline mode (pen and paper) .
Then after 2 days i got a message from hdfc bank that my application for the millennia credit card has been declined. After that i wrote to hdfc complaint email, after a lot of back and forth from them, they still haven't provided the reason for rejection. I needed to know the exact reason why it was rejected so that i can know if it's some mistake or what i need to do to correct it.
It's been a month still no resolution, all i got are lame excuses like we don't know or can't tell.
Very much disappointed with the bank and thinking of closing my account with the bank.
My application reference number is 22B[protected]NS