My son received the Coby MP826-4G as a gift from someone for Christmas. It charged one time. We downloaded video and songs and he was able to use it until the charge went out. We have charged it for days and days. As soon as we turn it back on, after it says it if fully charged, it dies within 2-3 seconds. We don't have a receipt to return it. I do know that it came from amazon. What should we do?