I had a legit call a few months ago from the CRA (Canada Revenue Agency). He was nice enough and sounded calm, and I explained that with all due respect, since he called, I have no way of knowing if he is a scammer or not, so I'd like to call back. He was somewhat taken aback, but not annoyed. I asked where to call, and what to say to get to the matter at hand. After hanging up, I looked up the number, called them back, and got the issue settled. But I was truly surprised that he expected me to talk to him when he called. The CRA is probably the number one pretend-caller in Canada (Or two, after the RCMP - the federal police), so I was surprised they do not employ this as a standard practice and education for people to protect against scam calls. I was lucky to keep my wits about me, and that the call indeed was legit, but it shows there's a huge opening for scamming less savvy people.