Can I stop a buyer from submitting orders?

[tictac7]

I have read on an old post that it’s not possible. but did they add this feature?

I have this buyer that keeps asking for changes and modification to add things that he never requested on the first place, although I asked him multiple times to give me the information all at once, it’s like he keeps sending msgs every time he remembers something AFTER delivering, it’s really annoying, he’s a continuous buyer but I no longer want to tolerant his behavior! why is declining modifications is no longer possible!