Issues with battery on iPhone 4s.

Hey guys.

So

I'm aware of battery issues, recalibration and such. I'm trying to recalibrate my battery however, when it gets to 100% and I do a hard reset, I use it for a bit and it turns off around 70% and shows the charging indicator. I plug the charger in and the phone starts up at 1% and then charges up to 100% a few hours later. This has happened twice. The battery has been check twice and is showing as completely fine. Any ideas?

The Apple support chat guy told me to restore the iPhone and set up as new which I did yesterday, so far nothing has worked.