Good afternoon AinaxAlp,
Welcome to the Apple Support Communities!
I understand you requested to trade in your iPhone, but changed your mind. The resource below explains how the Apple Trade In program works, and what to do if you change your mind. I've highlighted some key information here for you. Click on the link for complete details.
Apple Trade In Program
"Can I cancel a trade-in?
If you haven’t yet shipped your device, you can cancel your trade-in by simply keeping your device.
If you’ve already shipped your device, the trade-in can’t be canceled. If you receive a revised trade-in value after the inspection of your device, you can then choose to reject it.
How does it work?
Whether you’re making a purchase or not, we’ve made it easy to trade in an eligible device either in a store or online. Just answer a few questions regarding the brand, model, and condition of your device. We’ll provide an estimated trade-in value or a simple way to recycle it.
If you accept the trade-in estimate in the store, we’ll give you instant credit toward a purchase or a gift card you can use anytime.
If you accept the trade-in estimate online when you purchase a new Mac, iPhone, iPad, or Apple Watch, we’ll arrange for you to send us your old device. Once we receive it, we’ll inspect it and verify its condition. If everything checks out, we’ll credit your original purchase method and send you any remaining balance on an Apple Store Gift Card via email.
If you choose to trade in your old device online for a gift card, we’ll also arrange for you to send it to us. When everything checks out, we’ll send you an Apple Store Gift Card via email.
Regardless of how you choose to trade in, if the condition of your device doesn’t match what you described, a new estimated trade-in value will be provided. You’ll have the option to either accept this revised quote or reject it. If you reject it, your device will be returned to you at no charge."
Enjoy your day!