HDFC Bank Credit Card

I suggest you switch up your strategy a bit. Use UPI for small purchases since it's free, and save the Millennia card for bigger buys to get 5% cashback. The Indulge card really only makes sense if you’re spending over ₹10 lakh a year; otherwise, it’s just a costly card that doesn't do much for you. It might be a good idea to check your statements every few months. If the fees are higher than the rewards you’re actually getting, it might be time to consider canceling it.

Contact HDFC Bank customer care, and explain this issue with them.

Thanks for the resolving my doubt. Now tell me what are the documents needed for the procedure of increasing the credit limit on my DCB card?

Verify that your card is active, online payments option are enabled also check that you are entering correct card details. Check all these reasons. And if the problem persist, contact HDFC customer support to resolve this issue.