I want to replace the back of my iPhone
I want to replace it with good discount
[Re-Titled by Moderator]
Not knowing your location this will get you an estimate. See “Other iPhone repair costs in the United States“ at https://support.apple.com/iphone/repair/service for cost if it’s just has the one year limited warranty.
Then “What if I have AppleCare+ for iPhone?“ > “Other damage (AppleCare+ service fee)” if it has AppleCare+ at https://support.apple.com/iphone/repair/service