How do I get a refund for an app subscription I cancelled months ago?

The plant identifier app was only a free trial there a charge I can’t get rid of on my site I canceled that along time ago an it’s still trying to charge me I even removed the app from my phone an it was never even used can you remove it please it has 2 month of service on there an so it won’t take none of my cards

[Re-Titled by Moderator]