Regarding return of Sign-On Bonus

Hi , I joined a MNC this year in Jan, but due to some medical condition I had to leave that company back in March. As per the company policies I need to serve 2 months notice period or as per the decision of my manager, so I explained my situation to my manager and after my resignation got accepted I left the company. I got mail few days later that my resignation has been officially accepted & my full and final settlement will be provided within 45 days , I waited for few more days but I did not recived any kind of mail from the firm . So I sent them a mail requesting for my F&F and exp letter along with relieving letter and got a reply from the company that I owe them an amount of 80000 Rs which needs to be immediately paid in order to clear the dues. Actually I got a sign-in bonus of 90000 from the company. I looked in the contract as well and they have specified below condition in the contract regarding the bonus Sign On Bonus You are entitled to a Sign-on Bonus ("Bonus") as set forth in the compensation breakup given herewith. The Bonus amount may be paid in one time lump-sum payout or in installments, and will be paid to you upon joining the Company. This payment is conditional upon your being employed with the Company for a minimum period of one year from the date of your joining, unless a longer duration is specified in OTHER COMMITMENTS/CONDITIONS section. In the event of your separation or termination from the company prior to the completion of one year or the period specified in OTHER COMMITMENTS/CONDITIONS section from the date of joining (whichever is later) for any reason whatsoever, you agree that you shall return the entire Bonus to the company, inclusive of the tax deducted. The company shall also be entitled to take the Bonus into account for reconciling any amounts due to you from the Company. Any such deduction from amounts owing to you by the company upon separation/termination as aforesaid shall not affect the Company’s rights in law or equity in respect of the amounts of unrecovered Bonus, if any. The Bonus shall be subject to all statutory deductions. All applicable taxes in respect of the Bonus shall be to your account. Kindly please suggest what should I do, as I don't have any job at present since my treatment is still going on, I waited for 45 days as per the mail i received from the company but they have not notified me regarding any kind of re-payment, so I spent that money for the treatment. Do please let me know what will happen if I don't re-pay them. If they in turn do not provide my exp letter or relieving letter than also I don't have any problem. requesting you to kidly have a look into this matter and let me know my options.