My Iphone 5 has a battery issue it will be at 100% then the battery will go down quite quickly then around 90% or so it will turn off and say it needs to charge il plug it in and it will instantly turn back on and be back at 99%. I tried bringing it to the apple store for a replacement battery but they said due to a dent at the bottom they couldn't open up the phone without damaging the screen. Is there anything else I can do? I saw something about recalibrating the battery? Would that benefit at all?