Can my company withold my salary if I resign without notice period?

I had joined an event company as a designer two months back and am in a probationary period for 6 months. I had informed HR during my interview that I will not be able to provide overtime beyond my working hours due to certain conditions at my home. I still am made to do overtime of 1.5-3 hrs on an almost regular basis without any extra payment. The company policies lays out the employee times of being from 10 AM to 6:30 PM for all employees but my shift extends way beyond the scheduled times and that too without any extra pay.
I have informed the HR that I will not be able to continue like this and offered my resignation but the management has threatened to with-hold my entire December month's salary if I resign and don't serve any notice period. Can they do that? What legal action can I take if my salary is withheld from me?
Thanks in advance.

EDIT : I should also mention that I had received a official list containing my companies polices and the firstmost point was that all employee timings are from 10 AM to 6: 30 PM Monday to Friday with grace period of 10 minutes.
But almost everyday I did overtime for them till 8:15 PM 8: 45 PM and even 9:30 PM without any extra pay and was supposed to show up in office at the mentioned time and not be late. This is the reason I had to take 5-6 leaves since my duties at my home were getting ignored and thus have decided to resign from this office. Now company is threatening to withhold my salary for which I have already worked If I don't work for the notice period mentioned in offer letter.