Issue with Unauthorized Chat Conversations in Teams without Teams license

Hi all,

We have encountered the following issue:

We are currently implementing Teams within our company. We have two groups of users: Group 1 consists of a few users with a Business Premium license, and Group 2 consists of approximately 200 users with an Exchange Online Plan 1 license for Exchange Online.

The problem we are facing is that Group 1 users are able to search for Group 2 users and initiate chat conversations with them, even though Group 2 users do not have access to Teams and are only listed as objects in Azure Active Directory (AAD). As a result, we cannot disable the "Teams" feature in the admin center.

Is there a way to prevent Group 1 users from finding and initiating chats with Group 2 users, or at least display an error message when they attempt to do so?

Thank you for your assistance.