Click Reporting > Calls to see the number of calls made, conversations, and received calls. 

In the top right, you can adjust the time period.

Note: Call reporting is available on Pro and Platform plans.

Call Columns

On the People screen, you can enable columns for the last call, calls made, calls received, first call time, and total talk time. 

You can filter these columns by Talk Time > 5 mins and Last Call more than 7 days ago for a list of contacts to follow up.