Thanks for the question. The following resources outlines troubleshooting steps if you are having issues charging your iPhone:
Battery does not charge from the USB power adapter
Important: Only original iPhone can be charged from a FireWire-based power source. If iPhone is connected to a computer that's turned off or is in sleep or standby mode, the battery may drain.
1. Verify that the outlet being used is working.
2. Try another USB power adapter if available.
3. If no other USB power adapter is available, try connecting to a high-power USB 2.0 port (not a keyboard). The computer must be turned on and not in sleep or standby mode.
4. Try another USB cable if available.
5. Also refer to iPhone and iPod touch: Charging the battery.