Hi Echoann,
Welcome to the Apple Community, where some of us do our best to help each other :)
Apple support have an article online for joining Apple Music.
Perhaps you will be more successful starting from there ?
https://support.apple.com/en-us/HT204930
I understand, with these free trial subscriptions,
if you do not want to subscribe afterwards,
they need to be cancelled within 24 hours of expiry.
(You lose access immediately on cancelling,)
How to cancel subscriptions from Apple
https://support.apple.com/en-au/HT202039
If you tried to cancel a subscription but you can't see it in the list
https://support.apple.com/en-au/HT212052
Cheers :)