Box account says storage is full, but I've deleted everything

Hi Stefan, 

Welcome to Box Community and glad to help! 

We've corrected your storage count. To verify this, log in to box.com> Account Settings> Used Storage. 

Let us know in this forum if you happen to experience this issue again. https://support.box.com/hc/en-us/articles/360043695334-Storage-Usage-Or-File-Count-In-My-Account-Is-Incorrect

Thanks for posting! 

That fixed it. I am still annoyed that Box does not have any means of contacting customer service besides a public forum post.