1 /5 ML: Not recommended for two reasons:
1. I think that Optus or staff from the Optus stall in Melbourne Airport gave my number to scammers because someone tried to scam me 4 times. Why do I think it started at this stall or caused by Optus? Because I lived in Australia for 1 year already and had my contract with Telstra before and nothing like this ever happend before. The message scam was a tourist visa scam and I also received a call (from a Melbourne number) that my data will expire that day - suprise I received today a message from Optus that it will expire in two days. Optus/the staff get your details from their sales there and they know how long you stay, maybe which visa type, etc.
2. The staff wasn’t honest about the bad coverage in WA, they told me I will receive 3G/4G - yes but only in bigger towns. Telstra is the only working network on the countryside.
I would avoid that shop- you don’t need directly data and can buy your simcard from Telstra in the city.

