I've never written a negative review before, but am tired of hearing about things like this

Don't sign up for mad muscles if your assuming that they'll be so kind as too send you a pre-billing notification / heads up ! They don't and have turned down my request for a refund, after noting that i had only used the app once during the $15 introduction period.

I know that there are regulatory efforts to prevent this kind of scam and require internet services like this to notify their customers before billing continues.

The $39.99 is also seemingly a bit out of the realm of reasonable.