You have two options.
1 - Under Monitoring/Analytics click Calling --> Detailed Call History --> (optional but recommended, filter by location) --> At the bottom of the page you can see the detailed call history where you can further filter by Calling/Called numbers. The date/time filter is at the top.
2 - Go to Monitoring --> Reports --> Run a Calling Detailed History Report for the time period you want and then manually parse the data for the extension in question.
