Iphone 3GS Faulty £50 ONE DAY OFFER!! ?

This is an iphone 3GS, black, 8GB 50 I GO ON HOLIDAY TOMORROW SO THIS IS A ONE DAY OFFER!!! FAULT - When I plugged it in the phone it kept saying - charging not supported with this accessory. The battery finally died and I have been unable to charge it since. Possibly a simple fix for someone who knows what they are doing. Screen is in excellent condition (NOT a mark on it), back is a little worn and has a very small crack at base where charger is plugged in, but it is only about 7mm long. originally locked to orange comes with charger. Based in Belfast area - Near Tesco, Newtownbreda.