Investment scam

Hi, i am an NRI and have been working outside India for a year now. Iwasnt sure what were the right investments to make. So i decided to go with a firm that was trusted by one of my friend. I invested with them for the past 1 year and on maturity i didn't take it out and reinvested. I have seen and heard other people get their investment money back so i didn't doubt it at all. Recently 4 months back the person i who i started investment went on sick leave and stopped working for some time. I had requested to withdraw all my maturing investments and they had agreed to it. Due to the sick leave and condition they had requested a month additional time and i agreed on humanitarian basis. But they kept extending the dates and all the schemes i have invested with them has matured. But they have extended paying it out saying financial and medical reasons. Its 4 months now and all i have got is 5000 from my 7.5lakh investment. And they are again requesting time saying they will pay out by given the circumstances and experience i don't believe it. At this point I'm not even looking for interest i just want my principal back. I don't want to loose it. I have documentation and chats as proof. But now they are saying i cannot legally do anything as they are willing to pay and they only have to pay when they want to. i don't know how to approach this situation. Any help would be highly appreciated. Thanks