I've caught on to this somewhat new strategy for sales calls - it's a recording that's made to sound very much like a live person by saying "hello?" to you when you answer the phone, then some line about "sorry couldn't hear you" or "sorry I had to adjust my headset" and then proceeding to their script. You can test this next time by trying to interrupt them and saying "hello!? hello?! excuse me, excuse me please" and you'll notice the person doesn't stop talking.