Unsubscribe an email address from receiving notifications for a Label
(string) LabelNumber (Required) - The label number to unsubscribe from.
(string) EmailAddress (Required) - The email address to stop receiving notifications.
(string) CountryCode (Rquired) - The code of the country in which the label resides.
See here for a list of valid country codes.
Successfull call will return 'True'.