Change Webinar Size, go over 500 atteendes.

I have a Occurrence webinar. When I set it up for the first time I had priceplan that allowed 500 atteendes, Now I upgraded my priceplan to a plan that allowing 1000 atteendes but my occurrence webinar that is 1 time every week still only have Webinar Size maximum 500 attendees. Is there a way to solve this or do I need to close this occurrence webinar and open a new one?

I would like not to open a new one bcs I dont want to change the linc to the meeting.