This situation is rare, but possible. If you only signed up yourself, you can delete your name from the tee sheet and pick a new tee time for your foursome. If you signed up multiple people, sign up the remaining person(s) from your foursome in another time slot to ensure they have a tee time. You can then email the Team Captain who created the Sign Up and request he/she put your foursome all in the same time slot.  Alternatively, players with Sign Up Genius accounts can also try to resolve themselves by requesting other players “swap” tee times with them.