Employer forcing 2 months' notice and deducting my salary after resignation

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 an employee to relieve me of my duty, even when I had mentioned that I will be serving the notice period. Later they transferred him back. Now they are saying that they will deduct the expenses incurred in the transfer of that faculty from my salary too.