Hyundai Santro — Poor quality and fraudulent practices

I had bought the car in October 05. I have got the car serviced a week back. I had spelt out very clearly that my car is not offering me the mileage promised. I had been given a bill of 5900 which i paid for the servicing where the repalced things like air filter, brake liners etc. I just checked the mileage and it stands at a dismal 8kms/litre. I was told that the worst that one could expect was 14. I feel absolutely cheated by the delaer and i see this as a clear case of duping. This is the second case of being robbed.
My inlaws bought a Santro car a couple of months back from the same dealer and we were told that we would be given a bonus of Rs10000 for gving up a maruti car and buying a Hyundai car. Unfortunately the sales rep forgot to punch these details while loading the order. I was told by their senior management that we could do nothing and blamed it on us.
These guys are pathetic at customer handling. I feel cheated and have vowed that will never ever buy a Hyundai car and shall dissuade people close to me from ever buying one.
I hope this does not go to deaf ears.