We are often asked if separate access permissions can be given to a channel. The answer is: No, not in the current version. Private channels are not available. Currently the permissions are configured for a complete team. All members of a team have access to all channels.
This feature is highly requested with more than 5,000 votes in uservoice forum. But it seems like Microsoft is working on it. Look at the comment in uservoice forum.
In an update on October 18, 2017 Suphatra from Microsoft wrote:
“I haven’t gotten a firm ETA from the team but I can say this won’t hit in the next month or so. Its a complicated feature, so it will take longer than that. I’ll let you know once I get a general date from them.”