Greetings, Lakshmi.

If you have already joined a college, submitted all documents and paid the admission fees then you will have to leave the institute officially before joining another college.

Most colleges have a cool down period of about 1 month where they allow students to leave for another college with 15-25% deduction in the money already deposited to them. Get in touch with your college and ask about the deductions as well as the procedure to leave.

Best of luck