My battery was not lasting as they said it should, and based on my symptoms, they sent me a loaner through AppleCare. Not the warranty, just their loaner service. See the attachment. They waived the loaner fee, and they sent this overnight, and even Saturday delivery, it was Friday. They sent the loaner, return label, even tape and a paper clip in a bag. How much better than Apple can you get?
This one is lasting the way it should. Call Apple tech support, give them the symptoms, then you will be forwarded to the iPhone specialists' department. Then give them the details you are dealing with, and they should send a loaner out and service yours.