Take the contract to a lawyer. Or phone up the tax department.
I can't tell you otherwise, as I havn't looked at the contract you signed with the dealer.
But I think that if there is a written amount for the final payment, then if they want to break contract and charge you a services tax, you can tell them that you'll pay the service tax, (GST), if they suck your balls.
yeh try that dude.. they will probably bite your balls off..
let me check the legislation & rulings... get back to ya dood.