Recovering a Microsoft Team:
In order to recover a deleted team, you will need to talk to your IT admin or Teams administrator. They will need to launch PowerShell to display all of the deleted Office 365 groups in Azure AD in PowerShell. You will then need to run a command to restore the specific id from the deleted group, and then verify that it was restored. For step by step instructions on how to do this click here.
Recovering a Channel from within a Micorosft Team:
To recover a deleted channel, go to the team name and click More options > Manage team. Go to the Channels tab. Find the channel in the Deleted section and click Restore. All the channel conversations, files, and tabs will be restored.