With league of legends there's just such an action. If you become a twitch prime customer, then you get something at league of legends. The first 30 days seem free, but I still have to sign in with my Amazon account. Unfortunately, I have not seen any specific information on Twitch, nor on other sites.
My question is: Do I have to pay for the next month and then can I cancel? Or can I still cancel in the free membership?
That must stand in the AGB's or under the offer in the small print.
Mostly you get a trial month and have to cancel 14 days before the end of the month, if you do not want to extend it.