There are a few exceptions to this rule. For example, if you are a student-athlete, you may be able to transfer to another university if you have been recruited by that school's athletic program. Additionally, some universities may allow students to transfer if they have extenuating circumstances, such as a medical condition or a family emergency.
If you are interested in transferring to another university before your first semester of your freshman year, you should contact the admissions office of the school you are interested in attending to inquire about their transfer policies.