BNM has a cool website to take in complaints from customers about their banks. This is the link to the site.
THE ROLE OF BANK NEGARA MALAYSIA (BNM) IN DEALING WITH YOUR COMPLAINTS
As a regulator of the Malaysian banking industry, BNM’s role is to ensure that banking institutions conduct their businesses in an appropriate manner and within standard banking practices. If your complaint does not fall under the scope of the FMB, and you are not happy with the decision and explanations given by your banking institution with regard to your complaint, you may wish to seek the assistance of BNM. You can use BNM’s standard complaint form which is available at all banking institutions.
Remember to submit your complaint with a copy of the “deadlock letter” from your banking institution.
I have a whole bunch of complaints on Maybank here. but I guess its not time to go to BNM yet.