Bank can be so inconsistent? this is very bad practice by incompetent HR.

exactly.
Company B - even before starting work pull a fast one on you, do you think the relationship can survive for long?

I once was also played by a big company
offer letter given to me, signed and returned
resigned in company X
Y retracted the offer letter before my joining date
very lucky X company was still trying hard to retain me with counter offers.

this taught me the lesson - big companies also cannot be trusted. they can preach so much about integrity, but action speaks louder than words.

good luck to you.

not MCO period.
unprofessional people can exploit you easily, need to be extra cautious.

last time I use to think only small company does this, then I realized big company also can do this type of shit.