Query regarding Service Agreement (Bond)- Please Reply soon

I Joined a well known BPO in the year 2013 December. I was not aware at the time of selection process that there is a Service Agreement which I need to sign and neither the HR told me for same. After I was selected I was given an appointment letter in which nothing was mentioned related to Bond. On my joining Date the HR Told me to sign a bond or else she will revoke my job offer. I requested her to allow sometime to think but she did not provided me any time to think . As I needed a job I signed a COE Based Service agreement in which it was written that In case I leave a job within a Year I need to pay company the amount of 75000 Rs. I worked there for a Month and after that fell ill due to night shift and long working hours. I sent my Resignation E-Mail for same to my Manager who did not replied to my Mail. Now Company is sending me multiple letters to pay Rs 75000 as training Cost and also got a Legal Notice from an advocate to Pay an amount of Rs 75000. My Concern is that I have not received any special training and neither I have been sent on OJT out of India for any special training due to which they are charging me this much amount. My Training was normal,just like any other BPO and I was also hired for Process Associate position which is the Calling Profile in a BPO. I and my family are very tensed and frustrated due to this Legal Letter and time provided to pay is 15 Days.I belong to a very middle class family and my father is retired Govt. Servant.Please save me ... I don't want to pay so much amount and don't want my family to suffer due to all this ... Please Help ...