I just had a solo trip. I even made reservations for up to 4 to find a reservation. I could not modify it, but I informed them when I checked in that it would be just one. Just make sure you actually show up for the reservation. If you make a reservation for 4 and don’t show, they will charge you the cancellation fee for 4. If you make a reservation for 4 and only one shows up, you will not be charged a cancellation fee.