You can change which Slack channel you're using by going to Account Settings > Integrations > Slack Setup > Click "Remove and reset all settings". Once you've reset your settings you will be able to set up an integration with your new channel.

You can change which Slack channel you're using by going to Account Settings > Integrations > Slack Setup > Click "Remove and reset all settings". Once you've reset your settings you will be able to set up an integration with your new channel.