What is the transaction of 39.99 USD. There is a mistake. So can you refund this amount please

we are a public forum of iPhone users.. we cannot refund you anything..

See if you have a subscription that you are forgetting about..

See or cancel your subscriptions - Apple Support

Or if you think something has been charged incorrectly

Request a refund for apps or content that you bought from Apple - Apple Support

Or.. if you are talking about charges to your Apple Card

If you see an Apple Services charge you don't recognize on your Apple Card - Apple Support

You are not talking to Apple. This is a user forum.