HDFC Bank emails customers about their accounts being upgraded to a Classic Banking or Preferred Banking without such an upgrade being sought by customers in writing or in another form. HDFC Bank also charges Rs.100 (+taxes) per quarter for this program and this is communicated as an opt-out in the welcome email.

So, not only is HDFC Bank upgrading customers without permission, but it is also charging them using a tactic whereby a customer's silence is taken as consent to be in the program and pay for it too. Why 'customer's silence'? Because the program membership is announced via an email (and sometimes a text message) - it presumes, without customer consent that they, by default, want to be in the program and are willing to pay for it. 

When customers do not respond to this email, the bank starts charging them a program management fee. The bank's corporate communications head clearly mentions this tactic in an interview with The New Indian Express.

See: http://bit.ly/2nhq5Lu - Quote: "Neeraj says that the bank ‘presumes’ that the customer would like to be part of the programme, unless they opt out of it"

RBI, through its Banking Codes & Standards Board of India (BCSBI), clearly and categorically prohibits banks from using opt-out tactic (also called negative option marketing). See: http://bit.ly/UnethicalHDFC (Section 11)