Why headphones are not working with my bold 9900?

I have recently bought bold 9900, & I have never dropped it or anything. but as soon as I tried the OEM headphones, they just wont work.

As soon as I insert the headphones, the volume bar appears & it keeps flickering between headphone volume & speaker volume, & i donot get any output on headphones. I have tried several other headphones but the same problem persists.

while playing the video, the same thing happens, as soon as I insert the headphones the video stops & volume bar appears, i try hitting play again but the video plays for 1 second & again same thing happens. The phone is not under warranty :/