Such voice messages are often of poor sound quality, due to cell phone being placed in a pocket or purse, but often can be clear enough for the listener to extract the main idea.
Lana: Ahm... ... Who told you?
Kate: I heard your whole conversation with Carol on my voicemail. You called me, and must have forgotten to hang up after I didn't answer.
Lana: F***! I can't believe it got caught on voicemail!