Since there is no App Store for Bangladesh, you must be setting up a fake account in another country's/region's App Store. An App Store can only use payment methods for that country. A credit card must be from a bank in that country with a verifiable billing address in that country. You can't use a Bangladeshi bank's credit card in another country's App Store.
Only Apple knows when it might begin doing business in Bangladesh.
M1 Mac mini, macOS 11.1; Watch, series 5 GPS/cellular, watchOS 7.3.3; iPad Pro 2nd Gen, iPadOS 14.4.2; iPad Air 2, iPadOS 14.4.2; iPhone 12 Pro, iOS 14.4.2; TV 4th Gen, tvOS 14.3 HomePods, audioOS 14.3 and Airport Express w/ Airplay 2