Help, my calendar is hacked and spammed!

There are “events” on my calendar I cannot erase and have not put there. They follow me around every day! I deleted the whole calendar and downloaded a new one. Still, there! At least in pocket calendar I could hide them but that means hiding a dozen every-single-day! It says they are read-only events that cannot be deleted. I have checked under privacy on my iPhone and there is nothing under Calendar that should not be there. And these events are all personal requests from people I don’t know that are not in my contacts.