Indane — AGENCY FORCING TO BUY STOVE

Sir,
I wish to bring forward a peculiar case in which the gas agency viz Benaka Gas Agency. i had gone to apply to Benaka Gas Agency, Rajaji nagar, 1st block, even they quoted me Rs. 4200 for a single Indane LPG gas connection. When i told them that it is not mandatory to purchase a stove from them, (referring to the display notice by Indane company itself in Benaka gas agency's office) the officials flatly told me that it's a common practice to displaying the board, and that the Indane Company has entered into a tie up with the gas stove companies, and that it is mandatory to purchase stove or else they won't give me the connection at all.
Today i got a letter from Benaka Gas Agency, which is also clearly indicating that purchasing a gas stove is NOT MANDATORY, just nominal inspection charges of Rs. 150 has to be made.
Currently i m having a private connection, hence i m having a brand new ISI marked stove, still i m being forced to pay 4200 against the nominal Rs. 1800. I don't know where to lodge a compliant as i feel the Indane officials have a hand-in-glove in this racket!!! please help.