Sarathi NGO Assam - No refund by Sarathi NGO

We contacted Amal Deka from Sarathi NGO in the beginning of November to hire a home care nurse for my critically ill mother (** years old, surviving with Kidney failure and a major heart attck).
He took money Rs. *****/- from us, and brought in a nurse who refused to stay with my mother and left in * hrs. Since then, he has been avoiding our calls, with no replacement, and no money return.
We waited till the **th Nov and then asked him to return the money.
He asked time till *st Dec, and again asked for more time till *th Dec, but still no return of money.
He tells us that he is a registered NGO and we can't do anything to him.
My mother needs Dialysis twice a week, which costs about **** in a week. The money that he took isn't less for us, it means we can get her dialysis for * weeks. My parents are retired Assam Govt employees. Father was in the agriculture dept and mother is a retired High school teacher. They live within their pension and savings. Please help us here.