Unable to get back my money from laptop dealer

I purchsed a 2nd hand laptop from a dealer in Kolkata in July, 2016 at Rs.13000. He gave me a written invoice in a paper. The laptop started having problems after 2 days. I returned back my Laptop to him and reached to an agreement that he will not return the full amount but will return me back Rs.10000. We made a written agreement as he said he was unable yo pay the amount at that time and he will pay me directly in my bank account provided in the agreement. After that I left Kolkata and I'm bangalore now. He still (25 sept, 2016) has not paid the money. Whenever I call, he says he cant pay. He is still doing his business in Kolkata. What can I do to recover my money??