Airtel — broadband speed is not as promised

I had requested for a new broadband connection online with airtel, got a call immediately from sales person from airtel showroom north usman road kodambakkam office and they have arranged a person called soundararajan to collect my documents from my office location. He came and collected all the documents and i had paid three months rental in advance to 500 rs worth installation free. After couple of follow up from me the engineer came and installed and said that i am given only 16mbps speed, since then i have been chasing everyone through customer care but no proper response and the speed remain same and they refused to take cancellation request also. I am frustrated to the core and would like to complain on airtel for cheating customer so cheaply and also refuse to respond to problems raised as well. Not sure how much support government is offering airtel but really bad experience in my lifetime. I would never ever recommend airtel broadband to anyone stay away