Has anyone ever switched between a university program to another?

I heard its the back door for students who didn't acquire their desired ATAR ranking for the degree.

Next year are my HSC exams, not this year, so I have time to work on my Assessment marks and study for the exam.

I would like to pick up Bachelor of Nutrition and Dietetics but the ATAR requirements right now are: Cut-Off 88.25 Median 91.00,
and I'm not feeling confident to acquire anything above 80.

Here are my Subjects (if it helps):

Maths Advance
English Standard

Any response about this would very helpful.