i have booked house for rs 2600/- and after 3 days it has been changed to 2630/-

Location/place: Bhandup Mumbai

Name of company/service: M/s Sai shradha Developer

I am amod i had booked house in badlapur west belavli builder name is M/s sai shradha developer (panvelkar group) on 12-03-13 for Rs.2600/- and after 3 days i got a call form builder office and they suddenly told me that we are going to cancel your booking i ask for reason they said rate have been increased and you have to pay 2630/- insted of 2600/- why this is happen once i booked and paid check
this is very painful this is happening only because of no control on the system..

i need justice