I would suggest to talk to those guys and explain them that you were planning to buy another car and thats the reason for putting up the Wagon-R for sale. And now you have some financial issues and have backed up from the purchase of the new car and hence want to retain your car. Don't spill the beans initially that you are ready for paying up the cancellation charges if any. Try to negotiate and if they are co-operative then you will not lose on anything, but if they are adamant you will have to pay up a nominal amount. Else if they sense that you are desperate to retain the car and are ready to pay some amount, they will make you cough up extra bucks. Get all the original papers that you have signed along with the original papers of the car back asap. Good luck, buddy.