Hi, my debit card expired last month and I have been trying to update my payment by adding another card but it keeps declining the card. I’ve tried several cards and it’s the same thing. What do I do?

See -> Change, add or remove Apple ID payment methods

Change, add or remove Apple ID payment methods – Apple Support (UK)

Add first the new card, then remove the old one.

👉 If you still need help, contact Apple Support.

It would take about 1 to 2 business days in order to process.

See the Apple Support article(s) below. Link to contact Apple Support in the article. 

Apple ID payment information - If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store*

Possible fixes.   Fix ‘Your Payment Method Was Declined’ Error In App Store.  -

                          Payment method declined in iTunes or the App Store.   -