My phone says it's charging but isn't!

My phone completely died so I plugged it up to my charger (which I had bought the day before) and the battery sign showed up notifying me that it was charging. I left it alone so it could charge. I came back an hour later and it still hadn't charged enough to power on. I left it plugged up for another 4 hours and it just stayed on the charging symbol. I moved the plug to 2 different outlets and I changed cords but it still won't charge!! Does anyone know what I can do to get my phone to charge?