What subscription do I have on my account that I can’t delete my card?

You also can't delete your only card if you are a Family Sharing Organizer.

See this article about updating payment methods on various platforms (iPhone, Mac, etc.): If you need to change or update your Apple ID payment method - Apple Support

"If you change your address, the credit or debit card information that you use with your Apple ID might be automatically updated by your financial institution, and you don't need to take action. But if there's an issue [such as you having a subscription or being a Family Sharing Organizer], add a new card first, then remove the old card."

Click on this link to see how to view (and mange) subscriptions --> If you want to cancel a subscription from Apple - Apple Support

On an iPhone, iPad, or iPod touch

1. Open the Settings app.

2. Tap your name.

3. Tap Subscriptions.

Review your subscriptions at Settings > [name on top] > Subscriptions. You can cancel them by following this link:

If you want to cancel a subscription from Apple - Apple Support