How to file a complaint on my friend for not paying back my money due to loss in bussiness

Actually we three of my friends have started a bussiness but due to financial problems they said that they dont hve the investment right now they will be paying it later. I have accepted it and have started our bussiness but due to bad luck our bussiness had been running in loss so we stopped running it. We have calculated the overall loss and shared the amount per person. They asked me some time i agreed and asked them to sign in the bond paper assuring that they will pay the amount but since they were not available they did not sign it. They have texted me that they will return the loss amount and told me not to worry about money. It happened around 6months back now they are saying that what is the proof that we are partners and saying we are not the partners. The bussiness agreement was also done on my name because the more investment was mine. I have the messages that they have agreed to pay the loss and also agreed to sign the bond paper but still delaying it. What should i do? How can i file the complaint?