Again, 'personal warranty' been manipulate by an irresponsible seller.
To TS, yes.. as dagger69 said, u will not have your money back from this kind of seller. Twisting words, knowing that he already got an advantage, knowing that police also can do nothing, hmm.. i really feel pity on u bro. Last time we also got one forumer selling a headphone that also use this 'personal warranty' to escape himself been sold a faulty stuff, just exactly as your case.
My advise, next time if u ever feel like something not good with the deal, plz just leave it. Dont proceed. Yes, this is not a stuff that you can decide its good and working well just with a simple test, its need more then that to verify whether its good or not. I feel like for this kind of stuff, dont buy used items.
And to seller, my advise is dont twist your words. Yes, you win on this but plz dont twist your words, just imagine if this case happen to u. U said want refund, later said no refund. And my another advise is,
Nama dah cantik, Hilmi Guffran.. Sedap nama Islam kau.. muka pun hensem, ada tahi lalat pulak lagi.. tapi sayangnye.. tak bersyukur dgn nikmat tuhan, minum benda yang memabukkan.. dan bangga pulak mengaku..

This is not personal, this is more than that. Bertaubatlah.