4S headphone jack, poor fit

Hardware: iPhone 4S and supplied headphones

Summary: I've had the phone for a few weeks and just now tried the headphones that came with the phone. The port on the top of the phone will not accept the headphones all the way in.

Detailed explanation: I play music and am hearing it through the phone's speakers. I then insert the headphones and the speakers are still playing the music and the headphones are silent. I then push the headphones a bit harder into the port and they work. But if I release that extra pressure, they pop out again and the speakers take over. The distance I'm talking about with this extra applied pressure is ~1mm.

I've looked inside the hole with a flashlight and just see a small metal looking circle deep inside. Tried turning it upside-down in the event there was something stuck in there, and given it a little shake and a few taps to loosen any debris. Tried a total of 3 different headphones and they all do the same thing.

No go, no headphones with this 4S.

Any ideas?