iPhone 3G not charging and showing lightning symbol

I have been using my iphone 3g from 2008 Sept. I have used it in US for about 2 yrs and now I'm using it in India. I did not face any problems with the phone untill recently.

As usual, one month back the phone charge got completely drained out. So when I tried to charge it, the phone keeps on showing "Lightning" symbol, no matter how many hours I charge it.

So, I took my phone to a local repair person, after explaining the situation, he said it was a battery problem, so he told that he will change the battery but it is not a original so he cannot give any warranty Which I agreed upon and paid.

To my bad luck, even with the new battery installed, once the phone charge completely drained out, the phone showing up same "Lightning" symbol.

I took my phone again to repair person to replace the existing and put back the original battery which it used to have.

Now I have this phone not working and ligtning symbol showing up forever when I plugged in power.

Please help me in resolving this.

Thanks In advance

Nag.