There is a major failure with a product when: you would not have purchased it had you known about the problem/it is significantly different from the description/sample or demonstration you were shown/it is substantially unfit for its normal purpose/it is unsafe.

For purchases with major failures you may reject the goods and get a refund or an identical replacement.

Minor failures include small problems with products that do not fit into the major failure categories, for example, loose threads on clothing.

https://www.accc.gov.au/consumers/consumer-rights-guarantees/repair-replace-refund

CHANGE OF MIND RETURNS

In accordance with Australian Consumer Law, we are not required to offer you a refund for sizing, fit, change of mind, or returns. For example, the consumer guarantees do not apply if you got what you asked for but simply changed your mind, found it cheaper somewhere else, decided you did not like the purchase or had no use for it.

When you have a major problem with a product, you have the right to ask for your choice of a replacement, store credit, or refund.  

If we have misrepresented the product or provided an incorrect description, you have the right to ask for your choice of a replacement product, a store credit, or refund.