The topic you've mentioned seems to relate to adult content, specifically phone sex or erotic conversations in Tamil, which is a language spoken predominantly in India and Sri Lanka. The term "ketta varthaigal" translates to "dirty talks" in English.
Sivaji Ganesan’s characters often represented the "Ideal Tamil Son." Love was secondary to duty (family, village, mother). Romantic storylines were frequently tragedies—lovers separated by caste, class, or fate. The topic you've mentioned seems to relate to