Hide client to commercial

[geppettvs]

How can I disallow a user from gaining access to a client and the client’s stuff like invoices, proposals, etc?

In a previous version, if a user wasn’t named as a commercial into the client’s commercial’s area, he/she wasn’t allowed to see anything from the client, but in the latest 9.0.4 version, every single internal user can see everything, no matter what permissions I give in the user’s profile.

Thanks in advance.

EDIT: Just installed the latest 10.0.1 version and the same behavior is observed in this version.

[ariffidaali]

The rights for 3rd parties are:
Unless the 3rd parties are linked to user then they have access to those 3rd parties:

Third Parties Read third parties linked to user
Third Parties Create/modify third parties linked to user
Third Parties Delete third parties linked to user
Third Parties Export third parties
Third Parties Extend access to all third parties (not only third parties that user is a sale representative for).
Not effective for external users (always limited to themselves for proposals, orders, invoices, contracts, etc.).
Not effective for projects (only rules on project permissions, visibility and assignment matters).
Third Parties Read contacts
Third Parties Create/modify contacts
Third Parties Delete contacts
Third Parties Export contacts

[geppettvs]

I guess I need to reword my question and I am going to explain this way in order to expand the scenery so that people can see what I am experiencing and what I need.

We have two users, which we are going to call user1 and user2.

What I need

If user1 create a proposal, user2 should not be able to see the proposal. The same for an invoice or other stuff made by user1.

What I am experiencing
Everything user1 do, is visible to user2

The same thing happen no matter if user2 is not named as commercial for the client.

Thanks in advance.