If you remove the earbuds from the device and attempt to change the volume on the phone with the volume buttons, what displays on the screen? Do you see the word Headphones under the volume control? If so, then the device is stuck in the headphone mode. This can happen if the headphones are not used much. You may try plugging and unplugging the headphones a couple of times to try and clear the sensor that detects the insertion of the headphones. You can also try a reset of the device, which could electronically fix it, hold the sleep/wake and home buttons together until you see the Apple logo and then release. The phone will reboot. This will not affect any of your data.