Can't unlink old address from account?

I recently moved apartments and transferred my Xfinity Internet to the new address. My old address is still listed as a linked account , and when I click the "Unlink" button (located under Settings -> Linked Accounts), I get this error message: "This account can't be unlinked yet. You're still the primary user on this account. Please switch to [old address] and transfer your admin rights to another user before trying again."

The problem here is that I can't transfer admin rights to another user because I am the only user on the account, so I'm not sure what I'm supposed to do to be able to unlink the old address. Anyone ever run into this issue or discovered a workaround?