You will have to setup a report for each area code. The format
is the same as the example, the only change needed is the
field selection value.
Custom Report grouped by prefix per area code:
To create a new report, click on REPORTS > CUSTOM REPORTS
Click on the "+", now enter your report heading under Description,
example Call Cost per Area 031.
Report options : Summary
Select records : Today
Summary Report Formats : Call category
Order by : Group
Group by : Prefix
Maximum Records : 0 (for all records)
Field Selection : Number, like, 031%
(all numbers starting with 031 will be in report).
This report will only show calls made to numbers starting with 031.
Which will be grouped by prefix, showing total number of call and
the duration as well as the cost of these calls per call category.