Most likely you can just enroll in the new program like you would any other, and once that has been fully confirmed you can cancel the enrollment of your original program.
You want to enroll into the new one first and not the other way around as you will otherwise lose access to some of the systems as a student as the system will see you as not being enrolled in any programs.
However the advice I can give you is only of a general nature so I highly recommend that contact RMIT Connect either by submitting a ticket online under the "Enrollment" category, or in person at one of the help desks.
https://www.rmit.edu.au/students/contact-and-help/connect
