The chargeable subscription begins automatically on reaching the end of the free trial duration, to give consistent continuous experience. So according to Google, on the off chance that you would prefer not to keep utilizing, you have to cancel the trial before the first subscription starts.

The trial is an initial offer and is benefited through PlayStore utilizing your Google Account. A user can avail the trial just a single time. The trial and subscription are managed through Google.

If you subscribed to the trial through Apple iOS (through AppStore), here is the article.