Have you previously subscribed and then uninstalled? If so, this matches a bug on Google's end I've been trying to get them to fix since last summer:
https://github.com/simon-weber/Autoplaylists-for-Google-Music/issues/102. I'll bug the support rep again.
In the meantime, do you mind sending me an email directly (
si...@simonmweber.com)? One idea is that Google Payments still sees a subscription, and I'll be able to manually cancel it on my end. For that I'll need help to identify your order id, which we can work out off-list.