Tranferring plates on new car

Hey guys, been stuck on the phone over 45 minutes waiting for transport wa, so figured id have better chances asking here. Just bought a new used car for the first time and got the licence transfer fee in the post, over 600 bucks. Which i figure is typical.

What I'm wondering is, can i just order new custom plates with a new rego and not use these ones? If so do i still have to pay this? its pretty much the same price so id rather do that. Just nothing on the bill says thats even an option, and i was gonna get custom plates anyways.

Have pity on me, im new to being an adult lol. Only moved into my first house this year and didnt even know a lot of the stuff that came with that too. Seems like they just want money for everything!