Hi @Robyn555
The service fee is the fee that Airbnb charges for its sevices - it's a percentage of the accommodation cost and that's how Airbnb earns its income.
You as a host may not be liable for VAT on your own portion of the earnings, but Airbnb is liable to pay VAT to the Australian government for operating an online travel platform and chariging service fees. You'll see the VAT is calculated on the service fee only - it's Airbnb"s VAT liability and they are responsible for paying it to the government.
As a host you don't have to do anything further.