How does a family member switch from shared iCloud storage back to an individual plan?

Thanks for the reply, but I guess my question wasn't quite clear. In Apple support (see Share iCloud+ with your Family) it clearly explains how you can start sharing your storage with your family. It also tells us what happens to someone who already has a storage plan:

If a family member is already paying for their own iCloud+ plan, they can choose to switch to your plan or keep their own and still remain part of the family. When they switch to the shared family plan, they get a refund for the remainder of their personal plan. They can't keep their current plan and use the shared family plan at the same time.

So, a family member can choose not to join the sharing plan and keep an individual plan, but what if the do join then later change their mind? How would they switch back to an individual plan without leaving the family (so they continue sharing other subscriptions and services)?

It seems reasonable to expect it can be done, but I haven't found anything on Apple Support about how to leave a shared iCloud+ plan and go to an individual plan without leaving the family altogether.