We do not collect or processes any personal data nor do we send anything to third party services.
The app only sends your android call log to the remote endpoint that you specify. The call log is not used in any other way nor is it sent to any third party services.
The source code of the app is available for free and the behaviour can be checked by reading the source code at: https://github.com/MarkoBL/AndroidCallLogSync/