Tata Motors — indigo ecs mileage very low

Hi,

I have purchased indigo ecs in jan 2017. The mileage claimed by company is 25 for highway and 21 for city. But from the beginning my car is getting mileage of only 12. I had complained regarding this multiple times to the dealer where i got my car serviced, but they did not help me. According to them my car is working perfectly and they cannot guarantee mileage in city. I understand this, but isnt 12 too low? I got my car serviced 4 times, including engine oil change and filter change, still mileage did not improve. What should i do in this case as the dealer is not helping?
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