Why is Pfizer Vacine not available?

The Government reported in February that a total of 20 million doses of Pfizer vacine
will be available in Aus yet all the public vaccination stations in Brisbane are only offering
Astra Zeneca to the general public and reserving Pfizer for hospital staff.

If we are getting 20 million doses of Pfizer, then why does the public not have a choice?
Has the Government now opted for the cheaper/less effective brand for the plebs?

https://www.health.gov.au/news/10-million-additional-pfizer-biontech-vaccines-secured

20 Pfizer million doses covers 10 million people/nearly half the population so particularly
for 1b category, there should be a choice of brand, IMO.