How about you do a double degree in Commerce/Arts, and that way you can major in accounting + do what you want to do in Psychology?
i dont really want to do a double degree and with arts and commerce, the course is too broad and that means we have to do further studies and i really dont want to send a long time at uni unless if its necessary
This is a poor rationale and demonstrates that you haven't thought through the scenarios - which is fair enough as it is difficult to have perspective on tertiary pathways if you haven't been in the system or industry before.
The cost-risk-benefit of adding an extra year on to your undergrad in the context of uncertainty is very favourable. It enhances your qualification and gives you maximum flexibility and experience to choose. Such a double degree would allow you to try both disciplines in first year and change both of them, drop one degree, take up another etc, with no loss of time.
The cost-risk-benefit of picking one now with little idea of the disciplines and industries is much less favourable.
Alternatively, you could pick BComm and enrol in the 2 x 1st year psychology units and see how you like them. If you really like it, then transfer to BA/BComm after first year and have the units studied previously credited to the new degree. This would require some careful subject planning to ensure you dont have to add another semester do to course requirements and prerequisites, but it's done all the time.
Still, seems much easier to me to just enrol in the double degree.