Only download the bank's app from the link on the bank's official website or from the bank's verified page on the App Store or Google Play.
Steps
Check the developer's name, the number of downloads and ratings, and make sure the link starts from the bank's website itself and isn't an advertisement or WhatsApp message.
If you're unsure, manually open the bank's website in a browser and then navigate to the app link.
Never enter your username, password, or OTP into an app whose source you haven't verified.