If you decide to read based on the date/time range, set the query parameter perPage to max 1000 to read more. Pay attention to the paging information from the response to read next page if there are more than 1 pages.

Alternatively, use the sync user call log or the sync company call log to import.

Check this link:

https://forums.developers.ringcentral.com/questions/329/exporting-call-log-data.html

Explained in details of using the setting perPage and dateFrom & dateTo filter parameter.

It also suggest you to make separate request each time as there is a pagination in response.

Also it says " Call Log is a "Heavy" Usage Plan API which limits your requests to 10 per minute "