Then you should just go to immigration. Make sure you have all your documents together and it shouldn’t be a problem. You just have to submit them and then come pick up your result 30 days later.
Tracey, when I changed mine I didn’t have to leave the country. I just applied for the extension at immigration. I did have to have 30 days left on my visa though.
Have you done a 30 day extension on your current visa already? I just did that and applied for my non o right after. No need to do a visa run if you are able to do this.