Hi @whitemittens you should check you haven't run out of airtime credit here https://giffgaff.com/dashboard
If you haven't try turning airplane mode on and then back off.
Receiving texts while in Australia is free - but ALL other usage is expensive eg. calls are £1 per minute to make or to receive, texts are 30p each & data is 20p per MB. So double check that you have not already used all your credit.