Trying to change primary email address to new address!

Frustration has set in. My "Manage account" shows my email address  as primary but I need to change it as I am losing that email address. When I try to change it to the new one, the system tells me the account already has that named address, even though it is a new address and not the one shown as primary.  In trying to talk to support via chat, they tell me that my old email address that I need to change is NOT listed as one that has an account associated with it. If that is the case, why would it be listed as PRIMARY email and the new one I am trying to use, they say I can't use because it is already associated with the account. Which I can't find it associated anywhere!! So confused!

[Mod: Moved to the Account, Payment & Plan forum]