If you see a charge from the UCSD Bookstore on your student billing, it is most likely related to the Inclusive Access Program where you received instant course materials on day 1 of your inclusive access course. Students had the option to opt-out until the add/drop deadline of the course.  For more information, please read

https://www.ucsandiegobookstore.com/inclusive-access-program

To find out which course the charge is related to, you will need to contact the Bookstore directly by calling them at 858-534-4557 or email textbooks@ucsd.edu.