Change mobile phone on Teams contact card

pazzoide76 

There's nothing you can do about that from an AAD Connect (and therefore on-premise) perspective.

Microsoft has formed some "interesting" ideas about sources of authority over the past few years, and this is especially true for the mobile phone number. From the article linked below, we have the following statement:

Mobile attribute with DirSyncOverrides

When the Admin uses MSOnline or AzureAD PowerShell module, or if the user goes to the Office Portal and updates the Mobile attribute, the updated phone number will be overwritten in AzureAD despite the object being synced from on-premises AD (also known as DirSyncEnabled).

Together with this update, Azure AD also sets a DirSyncOverrides on the object to flag that this user has the mobile phone number "overwritten" in Azure AD. From this point on, any update to the mobile attribute that originates from on-premises will be ignored because this attribute will no longer be managed by on-premises AD.

A support engineer can file an internal escalation request to revert the mobile SoA to on-premises by providing the objectId of the target users. However, this method is not recommended because this issue might occur again if a user or admin updates the Mobile attribute in the Office Portal or through PowerShell.

Troubleshoot Azure AD Connect objects and attributes - Active Directory | Microsoft Docs

In short: once "mobile" is mastered by the Office profile, you cannot roll back from that being the source of authority for "mobile". You will see Azure AD's "mobile" reflect what you see in on-premise Active Directory, but this AAD attribute is not the same as the "shadow" copy stored and used by the profile, which in turn is what you see manifest in Teams.

Cheers,

Lain