Company not paying manpower charges(recruitment fee) what to do

 In the month of February 2017 I was been approached by one of the CRO in Hyderabad to recruit 50 people for their team and I was happy about the offer and reduced by charges close to 3% as it was a bulk requirement and toiled hard for a month and sent close to 100 profiles and lined up close to 50 candidates for interview. To my utter surprise, they have selected only 3 and recruited 1 till date. Rest 2 didn't see the light of the day till now. So, this 1 selected candidate joined on March 6th 2017 so he completed 5 months till date. Actually, they were supposed to pay me after 1 month, but they always delay saying me some or the other reason. The amount is not huge but I want them to realize the hard-work we have put our precious time we have invested. So I want to proceed legally. What are the steps and how should go about it to make them understand the pain of an agency.