I tried to find a freemium option that didn't require me signing up or agreeing to spend $3.99 at some later date. Could be helpful to get more people deeper into the "funnel." Like maybe open up the first 1/x of one of the 22 lessons?
If that option is there I couldn't find it so consider that a single-user usability test or just user error.
This is a great use for privacy.com generated credit cards! Basically, you create a unique credit card number but set its budget to $1. They won't be able to start charging you until you raise the limit on the card. That's how I think all trials should work: requiring an additional confirmation to start charging you.
Also pretty ironic that this site is designed to trick you into paying for a subscription you've forgotten about...but that's the entire subscription/free trial economy of course.
If that option is there I couldn't find it so consider that a single-user usability test or just user error.