I’m unable to add my card for payments

If you already tried (to no avail) ALL the steps provided in this support article:--> Change, add, or remove Apple ID payment methods - Apple Support, contact iTunes Store Support Team using this link:--> iTunes Store & App Store – Get support for various issues, choosing: your country, then Apple ID, then iTunes & App Store. If your problem is not among the options shown there, tap/click on the option “the topic is not listed” and describe your issue.

Regards

Giulio