We can’t do this ourselves via Panel. Previously hosted domain names are in a sense “locked” onto an account. This stops us from playing the system - ie. letting our account expire then creating a new one (with another discount) and attaching our old domains to it.
If you own both accounts and your reasons for account domain switching are legit then Support can make the changes for you. Just explain your situation to them in a ticket via Panel, along with the changes you’d like to make.
Maximum Cash Discount on any plan with MAXCASH
How To Install PHP.INI / ionCube on DreamHost