Missing Teams Contacts after Migration

Hello,

We are currently migrating mailboxes from exchange 2019 to exchange online.
The migration works absolute flawless.

Now we have some employees complaining about missing teams contacts that were previously created in Teams only.
The MS support told me that this is a teams limitation and the local contacts are gone.

I know about unified contacts, thats contacts are synced now between outlook and teams and newly created contacts are stored in exchange online mailbox.

But whatabout the old contacts ?? cant believe that theres no workaround to keep this contacts.

Do you know something about this ?

Rene