I have two iPhone 6s's, both of which have serial numbers that qualify for the battery replacement according to this site: https://www.apple.com/support/iphone6s-unexpectedshutdown/ One phone is losing battery power faster than when new, typically dropping to 40% in a day with minimal use and minimal background apps running. The other phone is dropping to zero power each day under the same minimal use. I have not been able to confirm that either phone is suffering from a power-off issue when the battery starts to get low per se. So, if I bother to make an appointment to have these inspected at an Apple Store, how exactly will they "test" the phones? Will they simply look up the serial numbers to confirm that they have the bad batteries and replace them, or will they argue with me that the batteries are just "old" and the performance is within specs? The Apple Store is almost 80 miles from my house, so I would rather not waste my time if they won't resolve this.