I too got a call today that KYC documents need to be updated. Incidentally, I also got IDFC select credit card this week without any documents because I have a niyo IDFC savings account with aadhar KYC already in their records.
I also don't remember the docs. I think Pan Card and selfie. I won't be submitting docs when the person would call for a visit. I already have got IDFC select and also have axis ace which gives 2% cashback. So no need for this card. only metal was its appeal.
So on around 1st june they confirmed on email that there are no dues and they are cancelling my account. After few days I check the app and card was still shown active.
Emailed them on 19th June to confirm if the card has been cancelled, guess what? It was not and they processed cancellation on that email. So BEWARE of them.