My iphone 6s won't charge or turn on

Last night I went to sleep with my phone at around 10% while plugged in. When I woke this morning, it was at 1% and hadn't charged. I tried plugging it in a different charging cord that I know works with a family member's iphone but mine still wouldn't charge. I tried leaving it plugged in most of the day with no change. I have tried force resetting it by holding down the home and sleep/wake button for at least 30-40 seconds, but all it does is flash a low battery sign and a charging plug sign that tells me to plug my phone in. It is already plugged in. I have checked the port for any debris or lint. It is clear of all obstructions. I've tried plugging it into my PC hoping iTunes would activate it somehow. Nothing. A family member got a message saying there was a new upgrade for the IOS, would that have something to do with it? How do I get my phone to charge?