Hi Jewelofmac,
Welcome to the Apple Community.
Your Apple ID is the account you use to access Apple services,
like the App Store, Apple Music, iCloud, iMessage, FaceTime, and more.
You might want to check that your debit card is one that Apple can accept in your country or region:
Payment methods that you can use with your Apple ID – Apple Support
You would need to add the new debit card, before you would be able to remove the other payment method..
(ie: If you have subscriptions etc, you need at least one method on file at all time.s)
You could try logging-in to your Apple ID account online,
to add the debit card there:
https://appleid.apple.com
Or
How to 'Change, add or remove Apple ID payment methods – Apple Support
NB: If you have more than one payment method,:
Apple generally uses the payment method that is at the top of your list .
(You can change the order if you want.)
All the best :-)