Company trying to harass and extend my notice period

I had resigned on 9th Jan 2017 for which I got an acceptance saying 8th March 2017 (2 months’ notice period as per the company policy). In my notice period, I had taken a leave on 27th Jan 2017, which was an approved leave from HR head stating it will be a LWP. But now they are saying the policy has changed & now I must extend my notice period. Also, they have calculated 1 day extra saying I was absent on 16th Jan 2017 as well so they revised my last date to 10th March 2016, but I was present that day and I had mailed them the supporting stating my presence on that day but no success. Now, they mailed me on 6th March 2017 that my handover isn’t complete so I need to extend till 31st March 2017. I had already mailed them to start my handover, and had been following up on for a week & half but no one started the handover. Then the handover started on 1st March 2017. Also, when I said I can’t serve the extension, I got a reply saying that my salary will go hold on then. Need help.