Generally all offers will be till the last day of the month. But Dealer will always gets next month scheme on the first day of the month or at the max 2nd day of the month. In your case , he is trying to exploit you , since you have already booked he might think you are not going to cancel the booking. All the SE try to observe the behavior of customer like is it the first car of his life or second car. how much is chance of customer walking away if the deal doesn't workout n ..blah blah. ... I would request at you threaten him to cancel booking , tell other dealer is giving the same offer + some additional freebies . then he might budge.