Glow Premium Trial Help

Hi! I have a question about my 30 day glow-premium free trial. When putting in my Apple ID password to forward the process, it asks me if I would like to complete the $48 transaction. Will it actually charge my account? I was planning on cancelling the trial before it actually charged my card... I need help!!! Anyone who's done this do you have any answers? I know it's $4/month I just don't know why they'd charge me automatically for the whole year. Anyone whos done this before please help ASAP! Thank you :)