You can use the Control Center's search function to find 'Live' and 'Upcoming' Cable/Set-Top box content. If you simply run a search using voice commands and then navigate to the 'Live' and 'Upcoming' content tabs in the Control Center interface you can find 'Live' and 'Upcoming content'.
If you are watching your Cable/Set-Top Box input, you can use the 'Guide' button on Control Center remote to bring up your Cable/Set-Top box's TV Guide. Depending on your Cable/Set-Top Box provider, the button on Control Center remote may be located differently. Please see the article about how to Control Set-Top Boxes and the article on how to Customize Buttons on the Control Center Remote.