I put my dog on the phone. If I put the phone on speakerphone, she'll make these "muttering" sounds that apparently pass for human. Kind of a "om ow ow?" sort of vocalization, sounds like a question. So I just put it on speakerphone and set the phone down on the floor, she'll lay down and listen very attentively to the voice on the other end, and if they're quiet too long she'll ask her questions to make them start talking again.
It doesn't work all that often though, she has to be in the right mood for it or she'll just walk away from the phone (a fine solution as well). I've tried to catch it on video but she sees the camera and goes quiet...I guess she's shy!
She likes to "talk" to drive-thru speakers too! It's gotten me into trouble when I pull up and they ask me to wait, my dog will start muttering at the speaker and I've had people get a bit snippy thinking I wasn't listening, lol. "I said just a moment!" "Sorry, that's my dog talking, she didn't understand..."