Organisation deducting pay of 21 days as a shortfall in notice

I have resigned from the organization in a month’s time with a 9 days’ notice period and have not even accepted the appointment letter and completed all the exit formalities of the company and no were during my notice period or at the time I had given my resignation the HR person informed me that there will be a loss in pay due to short notice and as a layman I was in a opinion that since I had not accepted the appointment letter I am not binded for the 1 month notice period and the clause was not even mentioned in the offer letter. While following for the Payment I got to know that they are deducting 21 days as a shortfall in notice Do the company has a right to do so or I am at fault. Kindly advice