We are moving a client between plans. We have detached and import the mail domain fine. When we try and do the actual domain we get the message

Domain can not be deleted because it points to mail domain 
You can not delete domain, because it points to mail domain. It may be a mail domain right under this domain or the domain may be a pointer to the mail domain. Delete mail domain or remove mail domain pointer.

This process should not be deleting the domain or requesting that a mail domain is deleted as they are live services.
Got around this by updating directly in the database with
update ServiceItems set packageid = 742 where PackageID = 400 and ServiceID in (9,12,22)
update Domains set packageid = 742 where PackageID = 400