Duplicate Users in Sophos Central and Mapping user accounts to AD accounts - Azure AD Sync

We are trialling Sophos Central with a view to making a purchase really soon. Initially we didn't have any Active Directory Sync set up and user accounts were added to Sophos Central in the format Domain\Username automatically when the Endpoint protection client was installed. Today we set Azure AD Sync to import user and group information. This all worked fine and all directory information is now present in Sophos Central. However when logging in to a device which has Sophos Endpoint Advanced installed it shows the logged on user as the account that was originally created before the directory sync in the format Domain\username, rather than the Azure AD Sync usernames which are in the format username@domain.com. Effectively there are 2 accounts for users in the domain.

How do we get Sophos Central use the info synced from Azure AD to recognise the logged on user accounts rather than those that were originally created? The synchronisation of data from Azure AD is pretty useless if it can't recognise which user is logged on to a device. Can anyone provide any advice on this?

Thanks