Disable auto directory search in Teams, is it possible?

Good afternoon all 

I have created a second tenant for resident teams accounts so they are not attached to our own orgonisation. This was done so people could not see our staff within our teams environment.

All users have now been created but when starting a new conversation and searching they can see each other in the search options without typing a full E-mail address. Is it possible to disable to directory within Teams so a user must have the full E-mail address  or username to be able to initiate a conversation with one another?

Thank you in advance.