iPhone 6s won't hold a charge

What is the Battery Health / Maximum Capacity?

Settings > Battery > Battery Health and Charging > Maximum Capacity

Best Buy is an authorized Apple Service shop. 86% would normally indicate that the battery was replaced about 12-14 months ago.

Take the phone back to Best Buy and ask them to run a check on the battery. If you have an Apple Store in your area, you can take the phone there as well, but make an appointment before you go.

Hello again ~ I would take it back especially since it is at 86%. When you say fairly new…how long do you think since it was replaced?

~Katana-San~

Hello ~ That may be about right. Take it back in for a check and/or another battery.

~Katana-San~

Hello ~ Where did you have your battery replaced? Apple?

~Katana-San~