Can't add any credit card, even with correct details and money on card, "pending subscription"

Having continuous issues trying to add a credit card, have tried 3 different cards, all of which are valid and have money on them

I have entered the details repetitively, upwards of 20 times and every time it says it is invalid even though I am reading the details off of my card and double checking every time.

Start here, see -> Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

👉 fyi: Not all credit & debit cards seem to work with App Store / iTunes Store, try a different one, or preferably a credit card. If your card is not accepted as a paymenf method, you need to contact your bank.

-----

When I try to remove my card it says I have one pending subscription,

See -> Remove a payment method from your Apple ID

Remove a payment method from your Apple ID - Apple Support

⤵️

If you can't remove a payment method

If you have subscriptions like iCloud+, have an unpaid balance, or you use purchase sharing, you must keep at least one payment method on file.

• Do you have a subscription? You can cancel iCloud+ and cancel other subscriptions from Apple. When your subscription period is over, remove your payment method.
• If you're in a Family Sharing group and you use purchase sharing, the family organizer must have a payment method on file. If you're the family organizer, turn off purchase sharing, then remove the payment method.
• If you have an unpaid balance, you might not be able to remove a payment method. Instead, change your payment method.
• If you still can't remove a payment method, contact Apple Support.