This has nothing to do with the internet. I have never seen such fraudias anywhere. If what you are selling has a fault you are bound to tell it to the buyer especially when your stuff is repaired and you got it repaired yourself.
This guy aqgmbest or whatever his nick is a fraudia and should be banned. Also his complete IP range should be banned so that he does not joins this site in future.
Tumhe fraud kartay hoay sharam nahi aye? Atleast apnay nam ki he qadar kar lene the. Are you a muslim or not? Even our Prophet (PBUH) has said that while selling, you should tell all flaws to the buyer and not resort to cheating