Are you talking about this app?
Headway is a free app with Offers In-App Purchases.
1.
If the invoice has to do with an app that has a subscription associated with it, see -> Delete apps on your iPhone, iPad, and iPod touch -> Delete apps on your iPhone, iPad, and iPod touch - Apple Support
- If you delete an app, it doesn’t cancel in-app subscriptions that you might have. While deleting an app, you might see a Cancel Subscriptions option. Learn how to cancel your subscriptions.
If you don't want to continue a subscription you need always to cancel that subscription in time, see the following Apple articles:
If you want to cancel a subscription from Apple
If you want to cancel a subscription from Apple - Apple Support
If the subscription that you want to cancel is not listed
If the subscription that you want to cancel is not listed – Apple Support (UK)
2.
If you have received an invoice from Apple, on every invoice from the Apple Store and/or iTunes Store always states what you have purchased (and/or concerns a subscription) and the amount.
Tap on Report a problem on the invoice.

Or try to -> Request a refund for apps or content that you bought from Apple.
Request a refund for apps or content you've bought from Apple – Apple Support (UK)
If you have requested a refund, you must wait until Apple has approved. Then you will receive a message from Apple.
Refunds are not guaranteed. For more information, see the Terms & Conditions.
3.
Read also -> How does it work?
After you decide to begin your growth with Headway, you can choose the subscription period that fits your goals the most.
The Headway Premium subscription renews automatically at the end of each period (each week, month, 6 months, year, or otherwise, depending on the selected option) until you cancel.
Canceling your subscription means the automatic renewal will be disabled. However, you will still have access to all your subscription features for the remaining time of your then-current period.
Note that deleting the app does not cancel your subscriptions.
Terms of Use: https://policy.get-headway.com/info/terms-and-conditions-web.html
Privacy Policy: https://policy.get-headway.com/info/privacy-policy-web.html