Downgrading plans happens at the next billing cycle (30-days), until then the quotas of your current plan will be in effect.
Note: If you exceed any of the storage quotas when the new billing cycle begins your Spaces will be locked and you will have to delete files, folders or spaces that you do not want to keep. Once your Spaces are under the storage quotas, it will be unlocked again.
The storage quota limits include the number of spaces, number of files and folders per space, maximum file size, and total data stored.