Change primary email on our account

The primary email on our account belongs to someone who is no longer at our company.  (Username: mjmjoyce).  We have tried to go in and change the email to the proper person but it is not saving the change.  Can this be done on your end? j****@m*****gschurch.org is no longer employed. The email should be m****@m*****gschurch.org.  Please advise what we should do to make this change.

Thank you,

Madi Cona

The email address cannot be changed to "m****@m*****gschurch.org", because this email is used in another account(username: mcona) already.

Please try using another email address. Let us know if you need more help.