Emplooyer not accepting to release earlier and buyouts

I'm working with MNC in Chennai. I dropped paper on Nov 22,2017. Company have policy of 3 months notice period else buy out the remaining days. Manager accepted for my request and HR is not allowing me to get relieved before 90 days. I got joining bonus of 1 lakh and I need to repay them before relieving 12 months. I have office laptop and other peripherals in hand. Requested my HR Head saying ready to pay the joining bonus and remaining days basic salary through multiple email and meetings. Also asked them the procedure to surrender all company assets and amount payable details. They are not responding to my email after 3 reminders. I got aboard offer and have to go before Dec end. Marked my personal email in all mail communications and documented all mails in both soft and hard copies. I don't want service letter just need to surrender my office laptop and joining bonus. HR threading me saying legal actions will be taken against me suppose if I walk out on Dec 15. Kindly guide me how to handle this situation. I'm completely depressed and don't know to get rid of this problem. Please advice..