Check your spam / not important emails in Gmail…I got 1 free credit for being a member. Not sure what the eligibility criteria is and you should redeem the code to get a credit by 31st Dec
Email copy paste below:
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This promotion is valid until 31 December 2021. Eligible email recipients will receive a claim code redeemable for a single credit at https:www.audible.com.au/promo/redemption. Code must be redeemed by 31 December 2021, upon which code will expire and you will not be eligible for another code. The promotion applies only to items sold by audible.com.au. The same items sold by other sellers (e.g. audible.com, or audible.co.uk) do not qualify. Claim codes cannot be resold, transferred for value, redeemed for cash or applied to any other Audible account, except where required by law. This promotion may not be combined with other offers. Limit one per customer and account. Audible account required. Other terms and conditions apply, including those available at http://www.audible.com.au/legal-terms/Conditions-of-Use?modu… and claim code terms and conditions at https://help.audible.com.au/s/article/what-are-the-condition…. If you violate any of the terms or conditions, the promotion will be invalid, and the offer will not apply. Audible reserves the right to modify or cancel at any time. Any terms prohibited by law shall be void without prejudice to the remaining terms.
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From time to time I enrol for a trial, grab 1-2 audiobooks, and cancel my subscription.
Just a note: the same Amazon account can create different Audible accounts in different countries, they are independent - so basically you can get new books for each one of them, and switching between login country in the Audible app is quite easy.