This is becoming a huge problem on ebay where sellers are held to ransom over a product and are threatened with negative fedback if they don't do as the buyer wants. This is not a tragedy to those who only sell a few items but those who sell hundreds are month are always affected by bad feedback.
We do not always get the feedback we deserve and ebay staff are generally not very helpful when it comes to helping out.
People who often use these underhand techniques are interested in a quick buck and then they are off to use another ebay account and ruin it for the masses who have built up good feedback over years. These also tend to be the people who get most of their positive feedback by selling 1p items and falsely boost up the feedback.
I hope these words help you.
Please have a look in my ebay store for some excellent bargains.
Also, do not forget to give me a positive vote.