Hey LakeLadder,
We'd be happy to help you out with updating your payment method for your Apple ID so you can continue to successfully renew your iCloud storage space each month without issue.
If wanting to do so from your iPhone 12, you can use the following steps to update and add your new payment method:
Add a payment method on your iPhone or iPad
1. Open the Settings app.
2. Tap your name.
3. Tap Media & Purchases, then tap View Account. You might be asked to sign in with your Apple ID.
4. Tap Manage Payments.
5. Tap Add Payment Method.
6. Enter the payment method details, then tap Done.
All this info and more is available here: Add a payment method to your Apple ID - Apple Support
Keep in mind that if you're a part of a Family Sharing group, then the organizer of the group would need to be the one to update the payment method on file.
We hope this helps out.
Take care!