The app store already works like this. They clearly mark subscription apps like ...

cameronbrown · on June 4, 2019

But free trials are never really free: after 14 days when you've probably already forgotten about the app, your card gets charged. There needs to be a proper way to try stuff without slyly charging them.

Maybe ask them outright at the end of the trial if they want to carry on?

gbear605 · on June 4, 2019

That’s also already built in by Apple. Free trials don’t automatically turn into paid subscription unless you tell them to.