Breach of service agreement

Hello All, last year i got an opportunity to work with wipro bps in kolkata. I joined on 29 april 2016 and left 10 aug 2016,as i got a confirmation of my MBA,outside kolkata. Since then, my parents have been receiving letters from wipro, stating that i am supposed to report for my absence, then another stating i am terminated. Recently on 5th may they have sent a letter asking for full n final settlement of 13390. So, my father had no idea and i told him to avoid it as suggested by seniors. Now they have sent a letter thru a law firm stating i ll have to pay 13390+12%p.a within 10days or they will register criminal as well as civil case against me. This was my first job. And i had no idea about what is this. I haven't signed any bond,it was service agreement stating that if i left before probation period of 6month.i ll have to serve 30days notice period or a month's salary. Before leaving i just informed my team leader that i am leaving by 2-3days for my higher studies. Althou she told me about raising a DTS and i ll be absconded. But nothing as such has been mentioned by her. There were many others who left. But not received such letter, some have cunningly refused letters initially. But i am stuck, this is kind of threatening. I have not yet started my career properly. And such big issue. I cannot concentrate on my studies too.