Free apps requiring a payment for m being entered is not an uncommon observation. Several reasons are outlined in the links below such as outstanding balance or ongoing subscriptions. You can try to set up your account without a payment method but you may find there is no option other than to enter a valid payment method to satisfy Apple's requirement. If the item is free you will not be charged.
If you can’t download or update apps on your iPhone or iPad - https://support.apple.com/HT207165
- "You might need to have a payment method on file, even if the app that you want to download is free."
Create or use your Apple ID without a payment method - https://support.apple.com/HT204034
If you can't remove your last payment method or use no payment method with your Apple ID - https://support.apple.com/HT203905 - "Learn why you can't use your Apple ID without a payment method in the App Store, iTunes Store, and more."
If you still have problems Click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service --> "See a list of Apple phone numbers around the world." - https://support.apple.com/HT201232