I was busy at work when I got a calendar notification on my phone. I was baffled by that as I didn't have anything scheduled for today and when I checked, the notification didn't make a great deal of sense. I didn't have time to deal with it then so I just dismissed it and carried on working. I checked the Google calendar app when I got home and found that a new event had appeared in it, and that was what the notification was from. The subject was something along the lines of 'Notification 6438 - Your email has been selected' and it was set to recur every day for a week. It was very random so I checked online to find out what it might be.
It turns out that Google calendar is set to automatically add an event to your calendar whenever you get an invite, even if you don't accept it, so obviously this is being utilised by phishers and scammers!! It by-passes your email completely, and instead you get the notification directly on your phone. I had no idea that setting even existed, I think it must be new. I've since turned it off which did remove all the scam appointments from the web calendar. For some reason, it didn't remove them from the calendar app, I had to open up one of the appointments and delete them all that way which was annoying.
So for those of you who use Google calendar, especially the app, I recommend that you go and alter that setting now. There are instructions
here.