Move OU of a sync-user without delete frm Azure AD

Hello,

For the explication, i've one OU (we'll call it OU A) that's sync (on CloudSync) where i had two users that're sync.

When we have synchronize this two users we've push the sync with there distinguish name.

A few weeks later : 

I've moove this two users to another OU (we'll call it OU B) that's sync too (on CloudSync).

But suddently after the auto-sync (the one that pass every 15mn), it delete my two users from Azure AD (as i guess it don't find this two users anymore in the OU A).

So i had to remove my user to the OU A cause every 15mn they were delete from my Azure AD (even though i push the sync with the new distinguish name of the OU B).

So my question is, how I move an user from the OU A to the OU B without them being delete on Azure AD ?

Thanks.