Even though the buyer did not contact you before leaving negative feedback, the best thing you could have done was contact the buyer, apologize for the item not being up to the buyer's expectations (no matter if it really was or not) and inform them that you would be happy to accept a return of the card, will provide a return shipping label and will refund their money as soon as you receive the item back. If the buyer opens a 'Item not as described' case with Ebay and you decide to argue instead of immediately accepting the return and refunding the buyer (plus return postage), then Ebay will force you to refund the buyer AND allow the buyer to keep the item.
The time to discuss the removal of negative feedback is after you have reasonably corrected the situation.
Since you have dealt with this buyer in a semi hostile and vaguely threatening manner ( IE~ telling the buyer " I suggest you to answer me in the next 24-48hrs" along with your reference to having previously given the buyer a 24-48hr deadline), you are very, very likely going to be stuck with the negative feedback.
Some advice ~
Never argue about a negative feedback rating on your Feedback profile, it only makes the seller look bad. How a seller deals with unhappy buyers and negative feedback is often more important to potential buyers than positive feedback ratings. If you must reply to a negative feedback, state only the facts without emotion or opinion and only after the transaction has ended.
Also sellers should not post messages or return policies for potential future buyers in a reply to negative feedback. That is what the description area in listings are for. Again, that can possibly make the seller look bad.
