I register Apple music because it told me that’s free for 3 months but I was charged before 3 months I think I just use it for 3 days
This picture show that I should not be charged
iPhone 6, iOS 11
All that is saying is that if you don't manually cancel the subscription before the end of the 3 month trial you will be charged $9.99 from that point onwards. Unless you actually got a bill you haven't been charged, but by what you said I can't tell if you said you got a bill or not.