Apple one and iCloud storage
How do I request a refund for iCloud storage now that I have Apple one
Depending on what you signed up for, it will cancel on its own - What happens to your iCloud storage plan when you sign up for Apple One - Apple Support.
"If it's smaller than the storage provided by Apple One, it'll be cancelled immediately.
If it's equal to the storage provided by Apple One, it'll be cancelled when the Apple One payments begin.
If it's larger than the storage provided by Apple One, it won't be cancelled automatically."
(Learned from Niel)