Silencer gets rusting within 15 months even after good maintainace of the car.

I m driving my verna XI for last 15 months with extended warranty for 4 years with odometer reading about 10,000km.During september car underwent 3rd free servicing in Oja Hyundai, Guwahati.and as per the dealer car was certified perfect. Now few days back my driver noticed rusting over the silencer drum and water leakage is there. Immediately i took the car to the dealer and what i had been told there was quite astonising.According to them rusting is not because of any manufacturing defect but it is due to less running of the car.So from now onwards I shall have to run the car unneccessarily and burn fuel only to keep hyundai car in good condition. Moreover they have practically denied the fact that rusting of the silencer does not come under warananty cover for replacement. So i will have to bear Rs 9600/= plus labour charge every year to run verna b'cos rusting is due less running of car and i don't have enough time to run the car unnecessarily. I have enquired in a local Maruti dealer and shown them the problem they inform me that till now not a single SX4 has come with such problem and they would have certainly replace the thing under waranty cover without delay b'cos there is no dent or no sign of road traffic accident. Anyway I am waiting for the parts to arrive and the sevice manager of the dealer has written the matter to the company hoping to get reply soon. Now its not a matter of money but the matter of after sale service by the multi national automobile company to indians.So can anybody suggest. I am yet to write to the company waiting the reply i get from the dealer.  Good interior both look n quality, very refined engine, good road handlingPoor initial punch and very poor after sale service