Whenever you sign up for a free trial, if you do not cancel it in time you will always start a paid subscription.
Make sure you read what happens after the free trial ends before you sign up for one.
You can request a refund by following the steps in this guide:
Request a refund for apps or content that you bought from Apple - Apple Support
You are not guaranteed a refund tough.
This is an automated process, if you wish to explain your situation in-depth to a person you can:
Contact Apple for support and service - Apple Support
Also, see this:
How long refunds from the App Store or other Apple services take - Apple Support
Good luck!