samsung series 5 ultrabook audio problem

Hi,
I recently bought a samsung series 5 13.3" ultrabook, loved its looks and with good reviews, made the decision to by it. But, found a unique problem - when i insert a headphone in the jack and watch a video/movie the background noise is very loud while the actual lyrics /dialogues are very soft (almost not able to hear). otherwise, on the in-built speakers, there is no problem...

so, called the service guy, he first said the headphone is not ok. But i did not relent and called up a senior guy, who checked and then said we will replace it. So, next day the service guy came with a new motherboard!! and opened up the laptop, replaced the motherboard and checked...but the issue persisted...and now the service center people are saying that they are finding the same issue in other laptops of the same model and are offering me a refund.
but, i am not convinced...something else is wrong...if its a problem in all the laptops of this model, then we must have heard this somewhere on all these tech threads and reviews, but nowhere do i find any such problem being reported.
what should i do? take the refund and buy another brand (cant afford a ultrabook then, cause prices are too high in india) or take the refund and take a chance with another laptop of the same model
or is there some software settings, which are causing this problem.