Membership level storage allotment

I have a question for UNA, or anyone who has knowledge in this area. I have paid membership levels with storage space allocated accordingly.

Now, a paid member has 100G, doesn't pay, is sent back to standard which allows 10G.

He is over allotment, what happens now? If he tries to upload new content, what happens? Send a file in messenger, what happens?

I can find no documentation on this feature and what exactly happens in this real world case.

Thank you for your responses 🙏