You can have your iPhone battery replaced at Mac Business Solutions or any Apple Store for $29.
To have your iPhone's battery replaced, you must request an appointment through https://getsupport.apple.com
We cannot process appointments over the phone or help walk-in customers requesting this service.
How to request your appointment:
1) Go to https://getsupport.apple.com and click on the "iPhone" button.
2) Select "Battery, Power & Charging".
3) Select "Battery Replacement".
4) Select "Bring In for Repair" and enter your City, State and Carrier ...
5) Login using your Apple ID and select the phone you need to service.
6) Select a Location with an available appointment slot. If no slots are available you will have a to try at a later time.