If only the battery is defective, Apple can replace it for you.
If some other hardware of the phone is damaged, Apple can exchange the whole phone for a refurbished, new device. Since you're out of warranty, you'll have to pay for that exchange. Check this page about the price for your country and about whom to contact, in some cases the carrier can handle that as well as an Authorized Apple Service Provider.
Service Answer Center - iPhone
iPhone - Contact Support - Apple Support
If a non authorized repair shop does repair the phone and it does not work after that, Apple will not service the phone anymore.
Out-of-warranty repair service
If your repair isn’t covered by Apple’s One Year Limited Warranty, AppleCare+, or AppleCare Protection Plan, your iPhone might be eligible for out-of-warranty service. For example, liquid damage isn’t covered by warranty but might be eligible for out-of-warranty service. Some damage isn’t eligible at all, for example if your device has been broken into multiple pieces. See Apple’s Repair Terms and Conditions for complete details.
Read Apple’s Repair Terms and Conditions
Model |
Out-of-warranty service fee |
Battery service* |
iPhone 6 Plus |
$329 |
$79 *available only if battery fails Apple’s diagnostic test |
iPhone 6 |
$299 |
iPhone 5s, iPhone 5c, iPhone 5 |
$269 |
iPhone 4s |
$199 |
iPhone 4, iPhone 3GS, iPhone 3G, Original iPhone |
$149 |
Plus a $6.95 shipping fee, if required. Fees are in USD and exclude local tax. Pricing is for service through Apple. The final service fee we charge will be determined during testing and may be less than the service fee listed above. Pricing and terms vary for service through an Apple Authorized Service Provider.
copied from Service Answer Center - iPhone