As the organizer:
You are automatically voting "yes" for all the options available in the group poll. It is not possible for the organizer of the group poll to change or delete this automatic selection of all the options.
The organizer can also not make changes to, or delete, the votes of the participants.
As a participant:
You can change your vote by opening the group poll, and clicking on "edit your selection".
This will take you back to the calendar page, where you can make any necessary adjustment to your selection.
Click "submit your selection" to save the changes you made.
If you do not wish to select any of the options in the group poll, select "cannot find a time" when voting.
It is not possible to delete your participation completely