Hi Jenifer! Thanks for visiting planDisney.
Mistakes do happen! It sounds like when selecting your range of dates, you chose your check-out day thinking it was your final night. If you're staying at one of Disneyland Resort's on-property hotels, you can
change or update aspects of that stay online by visiting
My Hotel Reservations. In many cases, you can modify within 30 days or more of your visit without incurring any fees. Since your trip is just around the corner, check to be sure your changes aren't past a cut-off date that would prohibit you from making the necessary adjustments. Adding an additional night would also be dependent on availability at your Disneyland Resort Hotel, which isn't guaranteed.
I hope it's an easy process to add another night, but if you're struggling to handle this issue online or would prefer to speak with a friendly Cast Member from the start, please use the Hotel Reservations or Vacation Packages
phone line, depending on how you originally booked. They're always ready to assist in whatever way they can. You might just have to wait for a few minutes before being helped. Also, be aware that prices and terms may be different than when you originally booked.
I hope this helps!
Elizabeth