How to fix error "This Apple ID was created for a different country/region"

• What region is your device set to use at Settings > General > Language & Region > Region?
• Is that the same Apple ID used for your device at Settings > [name on top]?
• If you are part of a family sharing group, you may not be able to change your region.
• All payment methods must use the same billing address as the region of the device. You will not be able to use the App Store in a region where you do not have a supported payment method.

For more information about changing the region of your device, then review this support article. There is also the option to change the region of the Apple ID online:

Change your Apple ID country or region - Apple Support

By the way, there is no Bangladesh Store so you will pretty much be limited to the apps that are already on the device.