Sorry, telephone, mail for private stuff? Surely you jest! In this brave new world there are only relative degrees of privacy. Social media, careless computer use, likely worse. Short of limiting interactions to face to face contacts with folks you know, little choice.
A touch of Orwell's 1984
"It was terribly dangerous to let your thoughts wander when you were in any public place or within range of a telescreen. The smallest thing could give you away. A nervous tic, an unconscious look of anxiety, a habit of muttering to yourself – anything that carried with it the suggestion of abnormality, of having something to hide. In any case, to wear an improper expression on your face (to look incredulous when a victory was announced, for example) was itself a punishable offense. There was even a word for it in Newspeak: facecrime, it was called." (1.5.65)
Facial recognition hardware & software? Prescient?