I can understand how people would fall for this one. With 20/20 hindsight, asking for the member number is fishy - it doesn't actually verify anything. And when my bank calls me, it is always automated - I only get a person talking to me if I ask for it through the automated systems. So in a way, any actual person calling would be a red flag. But in the moment, I can see why it sounded legit.

My parents have taken their precautions against phishing to extreme levels. They don't speak into the phone when unknown numbers call. At all. If they choose to answer, they wait for someone on the other end to talk and then decide whether to speak or hang up. They have heard horror stories of people getting their voices recorded and replayed into automated systems, so if someone calls and asks, "Hi, Is this <name>?", they avoid even saying "Yes", and instead ask who is calling. It may be paranoia, but as the saying goes... just because you are paranoid doesn't mean that they are not out to get you.