iphone 12 calendar messages

Starting a week ago, I am getting several messages a day added as entries to the calendar, such as "Your phone might not be protected! Click to protect it!", "Click now to protect your priceless data!", or "Your phone data might leak! Secure it by clicking now", that seem to be malware. This has never happened to me in the past. What would have triggered the messages? Is there actually anything to fix on the phone? How could I stop receiving those messages? Thanks for your help