How correctly extract tar.gz file?

This problem usually appear when you or your customer export Call Data Records (CDR) from MOR GUI. The archive extension has .tar.gz . Usually when somebody opens such archive with archivator - the cdr file in .csv forward is displayed correctly, but if file was saved by user into his PC and later opened for review - occasionally incorrect file is displayed instead of CDR file. This is because archive's extension was changed from .tar.gz to .gz .