We want some users to be able to view all Contacts completely, but if the Contact is not assigned to them, they should not be able to edit or add any information to that Contact. They can only click in and view it.

The reason we want them to see all Contacts is that when they are developing new clients on their own, they need to first check in the system whether the contact already exists and who the customer belongs to. If the contact already exists, they won’t accidentally overlap with other salespersons’ clients.