Am extremely unhappy with the experience since pas...

Am extremely unhappy with the experience since past 2 years, they were good when the car was new & was under warranty,but now the customer relation is getting poorer & they sound to be negligent to the queries & are always in a mood to argue with the customer. My car is in warranty & also hold a valid AMC while submitting for service, still they have put up a maintenance cost of Rs 5k (The car is having no defects till date, & I have always promptly maintained the service schedule ONLY with Wasan service till date). This maintenance bill is ONLY for general service (Oil change, AC & misc service) with NO replacement of any parts & that too for a Tata nano(2012 Model). I was thinking of an upgrade to Tata Tiago through Wasan before going for this service but now after this I am thinking of NOT to approach Wasan for any future upgrade & car service. Could someone suggest a better service center in Navi Mumbai as I stay in Kharghar.