Yes, mails are being sent by Different banks to it’s users to refrain from using it’s cards/services for purchase of crypto assets:
Source: https://www.newsbtc.com/2018/04/07/no-india-not-banned-bitcoin-trading-government-confirms/
This is the reason Crypto prices being going downwards due to stringent measures by Banks & RBI.
But some relief comes in form of press release by leading exchanges of India Unocoin & zebpay:
Unocoin:
Zebpay: