Rent A Volcano - Demanding service charge within warranty period

I have purchased a water purifier from company RentVolcano in December ****. At the time of purchase they had provided one year free service (also written in payment receipt). Now, since **th Aug **** there is leakage from machine. Leakage is increasing day by day. Whenever I start it there is water all over on the floor, so now we cant start it. Due to this we we are purchasing drinking water.
We have sent all the problem details to their service number, but no one is responding. When I managed to call them with different number, they are saying that your service will be charged and you have to pay Rs. ***.
Why I have to pay when machine is in warranty ?