I was pretty bagged, so I decided to catch 20 winks during the lunch hour. Of all the times I would get a call about Amazon charging me $99 and pressing whatever number to speak to a representative, they chose this time to call. I was very angry at having the rest of my day tanked, so I called back the caller's number a few times until it was redirected to voicemail. It was a Koodo voicemail service.
Afterward, it occurred to me that spam callers might spoof the numbers of others. Google confirms that this is common. So I unintentionally became an evil harasser, and a rather primitive one at. It seems that there is no way to escape phone scammers. Blocking spoofed numbers doesn't seem to be useful.