IPhone 6S Battery is dropping too fast
I have a 6S. Just this morning, it went from about 90% to 10% from just listening to music, with the phone itself face down on standby. Then, after sending 2 or 3 texts, it was at 1% in less than 5 minutes. I got my battery replaced earlier this year, and it didn't do anything. My "max charge" is already 88%. I refuse to upgrade the device itself-- it's barely 3 years old. What can I do to get this fixed, and have the solution actually work? I'm sick of never having my charge last more than a few hours without worrying about plugging it in.
iPhone 6s