Need to unlink old Fios account with my cellular plan

I have spent 3+ hours over a period of multiple days being transferred around customer service. Wireless sends me over to Fios and vice versa, it should not be this hard!!!

I need to unmerge / unlink an old Fios account from my current wireless account so that I can connect my current Fios home account with it. There is no option to do this online, even though the old Fios account is no longer active. No one helps, no one knows how to do this, and yet it seems SO SIMPLE.  So frustrating. Can anyone help?