Cars24 Services — Fraud while car selling

I wanted to sell my father's santro car. They gave a price of 52k in hand, after negotiation they fixed a price of 70k in hand. I asked their executive to lock the price and start the deal. I gave my documents and they transferred 1k token money. But after sending token money they reduced the price by 6k.i asked them to cancel the deal but the executive did not cancel the deal. Today I received a sms saying i have to pay 6k to cancel the deal. Also, on their app the price now shown for the same car is 90k. This is a very serious type of fraud this company is doing. I have all the call records and chats with their executive. Why should I pay 6k for their fraud. I am willing to pay back the token amount they they gave. Please help me and rescue me from their fraud.