Account Representative

We have a business account with AT&T for AT&T Phone Business Advanced. Under this account we have three separate site aliases to help track which numbers go where. We simply need to cancel all services associated with one site alias as we no longer have that property. We are paying for a service for a property that we no longer manage. We have tried chat, numerous emails, and  numerous hours on the phone to no avail. Nobody can seem to help and it just results in getting forwarded to the next person who is not the correct person to help. We need to have an account representative who can help us navigate this as well as other account changes.