Rejected refund for PicsArt app despite purchase receipt

My son subscribed to the PicsArt app and activated the free trial for a week. After that, I received a message that an amount had been withdrawn from my balance. I checked the matter and contacted Apple support, but they refused the refund completely, despite the existence of a receipt for the purchase.

[Edited by Moderator]

Original Title: Why was the refund finally rejected even though I had a receipt for the purchase, the app wasn