Hi Mark,
Not sure if you're already doing this, but I found that you can include an External ID in the import (for both contacts and external organizations), which is used to identify existing records.
If the same External ID is used consistently, Genesys will update/link to the existing record. If it's missing or different, it can result in new contacts or duplicate organizations being created.
This might be worth checking, especially when working with larger datasets.
I found this doc helpful as well:
https://help.mypurecloud.com/articles/data-source-csv-file/
Hope someone from the community might have a different way to approach this as well.
------------------------------
Phaneendra
Technical Solutions Consultant
------------------------------