I lived with my grandmother as her caregiver for many years. She would listen in when I would talk to my best friend on the phone. She’d pick up the rotary phone in her room and just listen. My friend and I could totally hear when she’d do it and we’d stop talking and I’d ask what she needed. After she passed, my friend and I heard her do this a couple times more.
Also, the rotary phone would ring occasionally after her death, and after I had the house line disconnected and went to only having a cell phone.
The old phone is now in my daughter’s room and she plays with it.