If you previously used a free trial for Apple Music or belonged to a Family Sharing plan where you used Apple Music, you are not eligible for another. You can go to the Apple Music page anytime and it will show you the promotion offers, but the verification for eligibility is only determined when you attempt to redeem with your Apple Account. If you are not eligible, the authorization screen will show the price of the subscription, and if you are eligible, then you will see the free trial period and the date the subscription will start if you do not cancel.
Be aware that any website that offers a free trial will show it to you and they are all subject to the eligibility terms. For example, if you go to the Amazon start page you will see a Free Trial for Prime if you are not logged into your account. Once you attempt to redeem the offer is where the eligibility check will be performed and you will see that there is a charge to proceed instead of getting it for free. The same is true for other streaming sites such as Pandora or Hulu.
You can request a refund using the link below. In most cases all transactions are final, but at times Apple will provide a compassionate refund.
Request a refund for apps or content that you bought from Apple - Apple Support
