Charlie says that his old iPhone 6S is losing battery life. Leo says that the phone is just plain old. The batteries of mobile phones usually handle about 500 complete charges. After that, they start to degrade quickly. Unfortunately, Apple's $39 battery replacement deal has passed, and as such, it'll cost over $100 to get it replaced.
He bought a battery from Amazon, but the phone says it charges less. Leo says he might've bought a counterfeit battery from Amazon. Go to Apple. Pay the $100 and let the genius replace it. It's worth it.