How do I resolve the 'add a payment option' error when downloading apps on iPhone?

Re: "every time i download something it says i need to add a payment option

but when i do it says i need to add another one and now i cant install or update any apps

We are all Apple users. like yourself, in the community, so no-one here has access to your accounts or details to see what the situation is, that is causing you difficulty. We'd like to help, however.

Eg: Wondering if Apple Support's online article(s) can help you resolve the situation.

See what to do:If you can’t download or update apps on your iPhone or iPad - Apple Support

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Re: "I put in my debit card and it still doesn’t work and I’ve tried multiple things"

To check which payment methods that Apple can accept in your country or region:

Payment methods that you can use with your Apple Account - Apple Support

How to add an Apple Account payment method:

Add a payment method to your Apple Account - Apple Support

How to change an Apple ID payment method:

If you need to change or update your Apple Account payment method - Apple Support

How to delete an Apple ID payment method:

Remove a payment method from your Apple Account - Apple Support

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More trouble-shooting: There may be an unpaid order causing difficulty:

See: If a message says 'billing problem with previous purchase' or 'verification required' - Apple Support

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For help or support from Apple Support : (info. / support / contact options etc.)

✽ Billing and Subscriptions Website:

You can use the "Get support - start now" link (online chat / phone / email etc,) if you scroll to the bottom

Subscriptions and Billing - Official Apple Support

or

✽ Apple Account Support website: Apple Account - Official Apple Support