If you want to unsubscribe, according to the Private Policy of Apple, developers are not allowed to access to your subscription management. So you need to do unsubscription by yourself.

To cancel your subscription, simply follow the instructions below:

Also you can follow the link: https://support.apple.com/en-us/HT202039

How to request a refund:

Also you can follow the link: https://support.apple.com/en-us/HT204084