how do i cancel all future charges from one of my old devices?

shaunhugo wrote:

Hello. One of my devices has a monthly charge of 0.99 cents for icloud storage. How do I cancel that monthly charge?

Devices don't have charges, accounts do.

https://support.apple.com/en-ca/HT202039

That iCloud storage is being charged to your AppleID, not any particular device. If you don’t use that AppleID, you will need to sign in with it on some Apple device with that AppleID and cancel the subscription(s) tied to it.