Phone tapping
It is not illegal to “listen-in†on calls – so your employer or phone owner can record anything, whatsoever (if all calls are automatically recorded, an employer is supposed to provide a telephone where conversations remain private but again he can still "listen-in").
Strangely, the Police and security services have great difficulty in getting authorisation to intercept telephone calls or emails and can only do so for the purposes of national security (including the prevention and detection of organised crime). However, they have little difficulty in obtaining copies of telephone bills and details of text messages.
In any other circumstance it is a criminal offence for a third party (and that includes the Police if they are acting without authority) to intercept telephone communications.