3 months notice period payout issue - basic or gross

Hi, I was working for a multinational company in Gurgaon, registered office in Mumbai under Maharashtra State. On January 7, I have resigned from my company and they asked me to serve notice period of 3 months. But somehow I wasn't able to serve 3 months notice period. So I offered my 3 month basic salary, i.e. Rs. 37500 as notice period payout. But they asked me to pay 3 month gross salary , i.e. Rs. 1,50,000. But as per industry and as some one told me as per Indian employment and labour law , employee will pay his basic salary as notice period payout. Despite this my company have one rule, if they will terminate someone from organisation , so they will pay only one month basic to the employee. Now my previous employer threatening me if I didn't pay them 3 month gross they will show my status as absconded from the organisation and issue a termination letter. What should I do in this matter, pls guide.