How to free up iCloud Message storage?

I'm trying to free up space in my Icloud, and post of my storage seems to be taken up by messages, 27.7 GB to be exact. I've followed all the recommended instructions like setting my messages to delete after 30 days, I've deleted conversations and attachments, and this only reduced the number of messages in my Icloud down by around 400. It now says I have 69,729 messages in my cloud and I have no idea where they're coming from. I need a way to delete these thousands of magic invisible messages so that I don’t have to keep paying for more storage as a broke university student.

[Re-Titled by Moderator]