Just so that you are fully informed about your rights and obligations, this is what the ACCC has to say about these kinds of circumstances - it may be worth sending the link (posted after the text) to the seller, because it clearly shows what their obligations are as well. and what they stand to lose if they don't meet them:

Unsolicited products or services

When you receive products or services that you have not requested, this is called an 'unsolicited supply'.

If you receive unsolicited products or services:

• you are not required to pay for the products or services
• you are not liable for any loss or damage resulting from a supply of unsolicited services
• if you contact the business in writing, expressing that you do not want the products, then the business should recover the products within one month
• if you don’t contact the business, then the business may recover the products within three months from the day after you received the products
• you cannot unreasonably refuse to allow the supplier to recover the products
• you may be liable to pay compensation if you wilfully damage the products during this period.

If the supplier does not collect the unsolicited products within the above timeframes, you can keep the products with no obligation to pay.

You are not entitled to keep the products if the products were not intended for you, for example, the packaging was clearly addressed to another person.

https://www.accc.gov.au/consumers/sales-delivery/receiving-things-you-didnt-ask-for