Fraud by alleged RTO agent

Hi, I work in TCS and 2 months back I was transferred to Kolkata from Pune on a project. I went to RTO to get NOC for bike. An agent Named Amol came to me saying he will completed formality and asked 1400 as fee. I agreed and gave him documents. After taking documents he asked 1500. I paid. since then I have been following him up every now and then. First it was said that it will be done in 10 days. I went after 10 days and it was not done due to some paper issues. Again I went after 7 days. Next I have to leave for Kolkata. Since then I have been calling him everyday. I even asked to give my RC book and documents and keep money if you are not able to complete formalities. But he never responded properly. Sometime he would say call me after 10 minutes (after every 10 minutes),sometimes he would not pick up phone or will talk rudely and disconnect the phone. Once he even said that he has document but he wont give me..do whatever you want...and asked me to pay another 500. I even agreed to pay 200 and still he is not responding properly or giving documents. I am in Kolkata. I am not sure what to do from Kolkata to get atleast my RC book back if not NOC. Please advice.