IPhone 4 won't charge | ran out of battery while system resetting?

I had to sell my iPhone 4, therefore went into the Settings and did the system settings and data reset.
The loading symbols kept on spinning so i slept. When i woke up, it had run out of battery. Now it won't charge. I have tried other USB cables, tried other wall chargers and even tried to charge it using a USB port. Still no progress.

Then, go for the phone repair…