Rescheduling a recurring webinar

Hello everyone, 

We have set up a recurring webinar for our customers. Now we had to change the date of one of our webinars. The problem we are facing now is that our attendees were not informed about the change and have the wrong blocker in their calendars. Does anyone know how we can inform the already registered participants about the change so that the calendar blocker also changes?

Thank you, 

Laura