Changing an Apple acount when you don't have a phone account

When my wife passed away, I cancelled her account with Verizon. Later I realized that she still had a Pandora subscription that I wanted to cancel; and I read that I could cancel it through iTunes. BUT iTunes insisted on sending a verification number to her phone number - which doesn't exist! So I am caught in Catch-22 - so I can't log into her account.

Does anyone have any ideas how to handle this?