I go to a california state university

Because of medical problems I had to drop out after the first day of the fall06 semester and couldn't go the spring07 semester. So I took zero units for fall06 but they're still charging us $1500.. I think it might have been a mistake. A school would probably wipe that off when they realize I didn't actually go right?

Also do you think I have to do anything like re-apply for admission?

i want to go again fall07