Employer bond

I joined a startup, a food based startup in june 2016 in gurgaon only. At that time it was important for me to join it as i was jobless and it also seemed to me promising. I joined as a operations lead. I signed an appointment letter, which had a part stating that, "The company will sign a 6 months bond with the employee, in case of non fulfillment of bond, the employee shall be liable to pay the company 2 months salary calculating to INR xx,000. " . I signed the appointment letter but bot any other bond or any other document. the company was not able to provide any basic facilities, such as a proper ceiling fan or atleast a washroom. I got ill in the second month, had cold, then viral , later a stye in my eye and the prolonged fever has induced pain in my backbone due to weakness. Upon asking for a medical leave, i was denied stating that its not their problem. The company doesn't provide any kind of medical insurance or any other benefits such as a PF even. Now after doing this that i have resigned, i am recving call and msgs from them asking for the bond minwy.. which they insist me to py money. Pls help me, is there any bond eligible here, as I have not signed anything other then appointment letter.