How do you delete a mailbox from your Yahoo app on the iPhone?

I have an iPhone 8 running the latest version of the yahoo mail app (4.37) In the app, I can either "Add another mailbox" or add another account thru "Manage Accounts" I initially added my account as a mailbox through the "Add another mailbox" link. It added my account/mailbox but didn't load all my emails. I then clicked "Manage Accounts" and added my account. Going thru "Manage Accounts" to add my account shows all my emails. Now, I want to delete the mailbox that was created. However, I can't seem to do so. I even went through "Manage Accounts" to delete the account, hoping that it would remove both the mailbox and account but it didn't. I followed the directions on Yahoo's website but those instructions didn't work I also tried adding my gmail account (as a test to delete it) thru the Yahoo mail app as a mailbox. I'm running into the same problem, I can't delete my gmail account/mailbox either. Hopefully someone can help me. Thanks. UPDATE: Deleting the app didn't work. The mailboxes are still here. I also tried going to my Iphone Settings->Yahoo Mail->Reset All Accounts. Also didn't work. Both my gmail account and that rogue yahoo account is still there.