My 3gs is totally dead!

Hello everyone, I'm having trouble with my daughters 3gs. The phone will not charge and thus will not turn on. I have trawled loads of posts regarding the issues and tried all the simple things. The phone is not recognized in itunes either. The last and final time the phone worked was when she used a battery charger with it one of these 2xAA battery charger and she said it came up this device is not supported by this , or words to that effect. Since then nothing could that be a coincidence?

List of things tried

Reset with and without power

Docking station

Wall charger

Charging from PC

I have replaced the docking port inside the phone and still no joy!! I can see no visible damage or any suspect water residue.

What my next moves guys?

Any specific help would be great

Thanks

BT