You can Manage Subscriptions from the Settings menu of your Device as well. Please follow the steps below:

1. Open the "Settings" of your device

2. Scroll down and tap on "iTunes & App Store"

3. Tap on your "Apple ID"

4. Tap on "View ID"

5. Now scroll down a bit and tap on "Subscriptions"

6. Now tap on the app you need.

From here you can manage/cancel your subscription

 

Refunds:

Unfortunately, we as developers of the app, do not have any control over the payment and refund process.
 

To get a Refund, we request you to please contact Apple support here: https://support.apple.com/contact