Employer trying to deduct salary after Resignation, 2 months' notice

I sent my resignation to my employer on 11th July, 2019 on medical grounds. They have deducted a month's salary and kept it as security money. They were supposed to return that money to us in April 2019, but haven't. I have paid Taxes on that amount so they have to give it back to me. I requested them to relieve me within a month due to my medical condition and reimburse my Security money but they are saying that I have to complete 2 months' notice to get that amount. I asked them to show me the written 2 months' notice clause, but there has been no response till now. They had made us sign a One-sided agreement in Feb, 2018 but didn't give us any copy. I can't remember any 2 months' notice mentioned in the agreement. Also after resignation, they sent a faculty to my centre to relieve me of my duty, even when I had mentioned that I will be serving the notice period. Now they are saying that they will deduct the expenses incurred in the transfer of that faculty from my salary too.