[Resolved]  Indane Gas (Domestic Lpg) — faulty gas cylinder

sir
I sujit kumar paul on behalf of mother writing this letter to you for your kind consideration.
There is a gas connection in my mother`s name Binita Rani Pal consumer no.13470 with Murshibadad Wholesale Co-operative society, Berhampore(West Bengal)-742101 gas agency.
On 01Jun09 they have delivered a gas cylinder but didnot check the weight excusing that he did not bring the weighing machine.
On 10Jun09 when my mother put it in operation after 2-3 min.the flame went off. After comming back home I checked it out and thought that some problem with valve. Very next day I complained to the gas agency. They asked me to contact the delivery boy. After checking he told that there is no gas inside but it is water. I just astonished to his word, the dareness to which they are doing such mischives. When we asked him about it, how it happened. He simply denied the delivery.He simply told that he didnot delivered that cylinder. And now he brought the weighing machine and the cylinder is weighing 24Kg. Again when I approached the gas agency they asked me to put a complaint and also told that it will be fruitfull if the delivery man certify the same cylinder has been delivered by him, but he is denying. Delivery man also told me to pay the price of 6Kg gas, deficit of the 24Kg. cylinder and he will replace it with new one.I don`t know why I should pay for that 6Kg. which we didn`t used.
I am working in Indian Air Force presently posted in Delhi living away from home, now on leave and returnig to job on next week.So there is no one to do for my mother`s concern.
My point is that what are the steps I can take to solve the problem generated by them and for that we are suffering.And is there any way to prove that one has supplied any particular cylinder. I need your kind help and I will be greatful to you.