refund my money

How i can refunded my purchase from apps, like gradient ( Gradient: AI Photo Editor by Ticket To The Moon, Inc.

https://apps.apple.com/us/app/gradient-ai-photo-editor/id1466097469 )

Its took my money, I tried to use the simple ways to refund my purchase by apple support website, they're not giving back my money.

I don't know how to regain it.

please help me.