Nokia/ 6330 classic
Difference in repair charges

I have nokia 6330 classic purchased on 08/10, the volume switch on the side of the phone is not working properly, the switch is looking perfectly allright from out side as my phone is under warranty i went to nokia service centre at jail road, new delhi, they checked the phone and the switch is broken from inside and they asked for Rs.400/- for repair charges as it is my phone is under warranty i need not to pay any thing but they are saying it is not covered. same thing is being repaired by mobile shops for rs100/-., with warranty