Illegal Service Charges being collected by Sify Broadband Dealers

I have subscribed to sify Broadban for 48 kbps ( unlimited )...now the vendor concerned is askinf for an additional Rs.50/- as service charge apart from the Rs 613/-(i.e 556/- + 10.2% service tax )that we are already paying him...is he legally justified to take that amt? Isn't sify paying him any commission

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