Indigo Airlines — Excess baggage charge

I was travelling from Bangalore to Pune on 10th Nov 2012 on Indigo flight 6E-108, I had a check in baggage of 16.8 kg (weighed at home) but the weight machine at the Indigo counter at Bangalore airport showed it to be 26 kg and I was made to pay Rs. 1260 as excess baggage charge of 6 kg. I weighed my baggage again at a commercial weight machine after getting down in Pune and the weight of the baggage was well within the specified limit of 20kg. I want Indigo airlines to immediately refund Rs. 1260 and stop cheating passengers in this way. I also found that many of my co passengers on the same flight had a similar experience with Indigo airlines in the past as well. If I do not get a positive response from Indigo airlines on this matter, I plan to refer this incidence to Weights and measures department, Govt. of India.
Dr. Ruta Devanahalli