How to set up confidential data exchange between project executors and the customer under the control of the executor's management?

Question

Work organization

Advice is needed
I need a chat to communicate
Add an employee and a customer
So that the customer sees only those performers
who are not seen in the project Other participants and users
And it was possible to control the transfer of data and texts in this group / conversation
I have a slack program
Communication within the user group
For setting tasks, etc.
In order to be able to communicate with an external user, I add him to the program,
but he sees all users
.
I need a program to control participants in communication, etc. So that other participants (not involved in the project) can not be seen
, constant communication is needed
. The project is underway
And often questions
Skype thought. But we don't want to. So that there was direct contact with the customer .
Therefore, they began to use the
prog. But they jammed. Slack. how you add a user. he sees the whole team at once
. Not only. who is in the project group

Answer 1

Wrike

Answer 2

raise your hipchat?
But it will not be difficult to go directly with any developer if you want.