How do I change or cancel my storage add-on?

Settings > Storage is the control panel. Upgrading to a bigger package applies immediately, and the confirmation shows the exact prorated amount charged today before you commit; the renewal date does not move. "Cancel storage" keeps your extra space until the end of the period you already paid for. Downgrading is not available yet - the interim path is cancel, then buy the smaller package when the period ends.

If your data still fits the remaining cap after expiry, that is the end of it; if not, nothing is deleted and the 90-day over-quota lifecycle begins. A failed renewal shows a banner with an "Update card" link to fix payment in Paddle. If you subscribed inside a store build, the store bills you, so cancellation happens in the store's own subscription settings instead.