I cancelled the extra 50 iCloud. They keep asking for credit card to pay. It has been cancelled. Do I just let it go for non payment?

If you're sure you cancelled then the issue is there is an unpair balance that was never resolved. You don't want to let it go because then that can block your iTunes / App Store account entirely.

You can put back on a valid payment method so that balance gets paid off or get a $5 iTunes gift card card and redeem it on the account to resolve the balance without using a credit card.

I would be sure you've cancelled the active subscription, and that you aren't over the free 5GB storage limit level.

https://support.apple.com/en-us/HT207594

ItunesInfo wrote:

I cancelled the extra 50 iCloud. They keep asking for credit card to pay. It has been cancelled. Do I just let it go for non payment?

Who keeps asking for a credit card and to pay what?