new ios9 update will not let me change exchange email account to company name

After the iOS9 update under my exchange email account my email is now listed as @exchange.com instead of @mycompanyname.com. When attempting to change it the 'done' button is not highlighted so I can complete the correction and it then reverts back to @exchange.com. The issue with this is because by setting are @exchange.com when I reply all I am copied as because the email assumes my actual email is someone different then the @exchange.com