Traning/ Meeting Bond

Dear Sir, I worked for Swiss Multinational company is sales department. last year company has sent me to visit an exhibition to Germany for one week. They have made one overseas policy that if the employee is sent to overseas for Training/meeting/ seminar/ exhibition, then after returning back from overseas travel, they have to serve the company for next one year. If the employee fails to do that, the employee will end up paying full expenses to company incurred during the visit. Now I have resigned from the company and still 2 months are left for completing one year. They are asking me to pay back 1 lac 41 thousand rupees as full expense which incurred during the visit. I have not signed any training bond in any company letter head but given my approval on mail before my visit to Germany. Is it legal for them to take this money? I have requested them to charge money on prorate basis, since I served them for 10 months. But they are denying and deducting full money. Do I have case in my favour? I can sue them for it?