The phone company
The phone company probably isn’t listening in on or recording your conversations, even though they easily could. There’s no financial incentive for them to spy on you. But they do keep a list of everyone you call, how often you call them, how long you stayed on the phone, and possibly even where you were when you made the call. This is done for the purposes of billing, but it is also a valuable source of information for anyone who might be interested in tracking your movements, your relationships, or your lifestyle.