If you had a related table with one record for each phone number linked to this table, you could define a calculation field using Count to count the number of calls for each number. Then a find can specify only the records where the calculated count is less than a specified total. This makes it possible to limit the numbers by count, but if there are other criteria involved such as pulling up only the records for a given date range, this get's a bit tougher to do as you then have to include the date range in the relationship but it can be done.
An alternative approach using your summary report is to use the "reorder based on summary field" option to list the records with the most calls first. A looping script can start with the first record in the found set and loop though the found set until a GetSummary calculation returns a value less than the desired "cut off" point. Then an Omit Multiple Records [ Get ( FoundCount ) ] Script step can omit that record and all that come after it to constrain the found set down to just those phone numbers that you want for your report.
The first option is significantly faster to pull up with large numbers of records but the second option is much more flexible.
Hi, Phil. As always, thank you for your time and the advise. I did not understand the first option you suggested, so I went with the second option. It took me several try outs and some time to understand the logic but I got it. Very nice. Muchas gracias.