Unable to download WhatsApp to my iPhone

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Manage App Store purchases, subscriptions, settings, and restrictions on iPhone

Manage App Store purchases, subscriptions, settings, and restrictions on iPhone – Apple Support (UK)

Prevent in-app purchases from the App Store

Prevent in-app purchases from the App Store – Apple Support (UK)

If you can't make purchases or update / download apps, including free apps, you need to update your payment method or add a new one. 

If you can't connect to the App Store, iTunes Store, or other Apple services

If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support

-> If you tried all of the above steps and you still can’t connect, contact Apple Support.

Keep in mind:

WhatsApp requires iOS 12.0 or later.

Snapchat & YouTube requires iOS 12.0 or later.

Facebook requires iOS 13.4 or later.