Today I went into my Billing and Subscription settings and cancelled my free 6 months Apple Music subscription (still had 5 months left).
My goal was to prevent the auto renew/billing when those free 6 months would eventually pass, although I didn’t expect it would send it all into the void.
I also contacted support and nothing can be done because of their policy about free promotions.
Pretty sure it gives you a warning that your whole free trial will end, no?