Hi useracme4businesssys,
There could be a number of different reasons as to why you're having trouble changing your email address for your accounting firm. I understand that you've been conversing with Rebecca already, but the best option is to follow up with her (if the case is still open), or to give us a call at 1800 114 837, 8:30am - 6:30pm Mon-Fri so we can find out where the email is already in use in our systems.
Bonny