Main access to Contact Cards is from 
Global Data → Contacts menu, but alternatively you can access it from 
AI Scheduler → Scheduled Calls as well.
This option is very convenient when you need to schedule new call with the lead who was previously cancelled, while you're on Scheduled calls page.
Navigate to
AI Scheduler → Scheduled Calls from the left side menuSwitch between Upcoming or Past Call tab depending of where the lead is to which contact card you need to access
Apply Call Status → Cancelled events filter in case you need to access to contact card of a lead whose call was cancelled in order to locate the lead
Click on the call to expand and see Call details
Click on the contact email to access the Contact Card
Learn more about Contact Cards here.