I can tell immediately from the tone of the voice. It's always too cheerful. A pleasant speaking voice is important for basic communication. Sounding that cheerful comes across as completely fake. I just got one not 5 minutes ago and it opened with "Hi, this is Mary. How are you doing?" I said "Fine" just to see how bad the script was. Then it said, "I'm calling to help you --", which is when I hung up.
First off, if you don't identify the organization you are representing in the first sentence, I'm going to hang up on you, person or bot. Second, I can't stand that everyone asks how I'm doing. You don't really care, and I don't want to tell you. It's a stupid tactic that again just comes across as insincere and annoys me immensely. It's bad enough when people do it, but a bot? That's insulting _and_ absurd.
Fortunately, the AI bots don't respond quite quickly enough, and they completely ignore you if you speak over them. However, even if they were better, it would still obviously be a spam phone call within 5 seconds.