Contact Permissions by user

Hi, I've installed and configured Redhen and have a question.

In our use case, each user in a role "subscriber" needs to be able to edit, add, view and delete their own contacts.

I don't want to give them permission to the global contacts. I've noticed that currently it seems all users either have access to all global contacts or no contacts at all.

Can you suggest how I would achieve the above? Is it possible?

An acceptable alternative would be a permission where everyone in organization 'X' has access to all of that org's contacts (but only superadmins could see all contacts).

Thansk in advance!