Unable to download free app from App Store

Why, any error messages?

Writing an effective Apple Support Communities question

https://discussions.apple.com/docs/DOC-5931

You don’t download an app from the Apple store. You download it from the App Store. When you tap on an app in the App store there will be a “Buy” (for paid apps) or “Get” (for free apps) button. Tap on that button. You will need a valid payment method in the App Store even to download free apps. It is used for validation of you and your account in addition to being the payment method for paid apps.

This might be what you are seeing→How apps, content, and subscriptions from Apple are billed - Apple SupportiTunes Store & Mac App Store: About payment card authorization holds

I just downloaded a free app from App Store but an amount of ₹549 was reduced from my account as soon as I filled in the card details . Why?

I find no way to download an app from the apple store. I see no icons or any hints on how to follow through. I know there must be an easy fix, but it is beyond me.