I was billed without subscribing
A general note on charges in the Shopify App-Store so there is no confusion here - as this is quite a common question and point of confusion:
A charge for an app in the Shopify App-Store can only ever be created by store-owners / admins themselves. We cannot create/edit a charge for your store from our side - there has to be a user with billing privileges from your store explicitly confirming the charge (and 7 day trial) on the screen that Shopify presents after installing the app. If this is not confirmed by the owner then Shopify does not allow any app to charge the store.
Consequently if you see a charge on your account this means that the charge has been explictly accepted by you or someone on your team. Shopify keeps a record of the exact timestamp when a charge is presented to you and when it is approved as shown below: