I have not done this but try clicking on the visible name in the upper left of the screen, then click on your account in the upper right of the screen, then click on the party pay in the middle of the screen, scroll down under your party pay group and there should be a button that says "leave this party" or "leave party". I just don't know how this works for the 1 person who created the party. If that's you, maybe you should try it first to make sure you can leave your own party. There's lots of big groups to join.
luvbug is sharing good info with you. Here is some additional info from Visible:
"4. Once a party has been formed, you can choose to leave the party, but you cannot remove other members of the party."
You can't move them. You could advise the following:
1. Leave current party
2. Send them the link to the new party you would like them to join
3. Hold your breathe and see if they join the party you think they will
I did see this thread here:
As long as you are in any party of 4 you WILL be charged $25 as long as it’s 48 hours before your next bill date. You will not be charged $40!"
So maybe don't leave your current party less than 48 hours before your bill is due.
How can we communicate to the people in the party, there is no way for that I think.
If you know them personally just ask them to leave from their login and join big party with more than 1000+ members so you don't need to worry about anything.