Akbar Travels Chennai - Flight ticket refund money refused

Dear sir / madam
I am small scale travel agent. "Akbar travels Chennai " is my service provider, last month i booked * flight tickets from them, unfortunately the air Airline ( Sri lankan air) denied passenger to boarding due some agreement issue. The airline promised us that you will get full refund from you travel agency, but akbar travels not ready to refund us, they saying now tickets are non refundable ... kindly help me to get back my money from them.

Thanks and Regards
Manoj Kumar