Navigate to
AI Scheduler → Scheduled Calls
Locate lead for which you would like to edit contact information
Apply filters by clicking on "Filters Applied" button, if needed
Click on the Call to expand and see more details
Click on the "Pencil" icon next to contact email and new window with contact information will show
Edit data and hit "Save" once you're done
Alternatively, if you're already in 
Global Data → Any of the sections, you can access leads contact card and make edits, by opening a contact card, clicking on the three dots and selecting Edit option (learn more here).