How do I unlink a seller account from my own?

A fee months ago i did an account audit for another amazon business who gave my account limited access to their own. We ended up not working together and I still see their account linked to mine. They are not the most tech savvy so they just left it linked on their end as well.

How do I go about unlinking our seller accounts so I no longer see their account as a selected account in my seller central?