Buyout notice period

Hello, I am praveen I want ask a question to law of notice period. I am working in medical coding company, where I working from 21 Jan 2015 in 1 year contract, according the contract they signed me a blank cheque said that if I leave the company before completing 1 year then they Cash the cheque of amount 1 lakh from my account. I have completed now 1 year on 21 Jan 2016. I have resigned the company on 22 Jan 2016. I am not able to serve one month notice period so I want them they buyout my notice period. I agree to pay one month salary in lieu of one month notice period, according to my appointment letter it is clearly mention that my employment with that company is terminated any time by serving one month notice period or in the absence of notice period paying one Month salary in lieu of such notice without assigning any reason whatsoever.but they refused to buy this and M.D. said that I do not consider it and sent me following mail after my resignation. Dear Praveen, As you have acknowledged the fact that you owe one-month notice period to the company, which is clearly lacking in your case. As regards to your proposition of buying out your notice period in lieu of one month salary, we are not in a position to accept the same since there is a huge business dependency on your role, especially when you were on the progression of next level, vide your acknowledgment email, dated December 18, 2015. You have also acknowledged, by way of your free consent in the contract of indemnity, that The Company is bearing a huge cost in your training and development and expects you to stay with the organization for at least a period of one year from the date of execution of the said contract. It seems you are confusing the duration of contract of indemnity with the terms of your employment letter regards to the reason of your leaving, we have confirmation in writing that you are holding an offer from another company for last 1 month or so, which not only means that you have willfully concealed the fact of your all-of-sudden departure from your existing organization, but also you have shown no respect to the fact that you yourself had acknowledged taking on the charge for the new role vide your email dated December 18, 2015 and had kept the organization in dark while you were holding another offer. We have no objections in you moving on to another organization as that’s your fundamental right, but we expect you to abide with the terms of your contract of indemnity and contract of employment by serving a 30-day notice period from the date of your resignation. Given the circumstances above, we cannot accept your proposition of buying out your notice period in lieu of one-month salary. They said they have confirmation in writing that I have holding a offer from another company,actually they do not have. They are not giving me relieving or salary. Please help me to give best suggestions