Maintenance being asked for months before possession.

I own a 4 bedroom, hall, kitchen flat in a society build by well named and established builder. I was provided possession of the flat in August 2012. But as i spoke to the 3 party service provider of the maintenance of the society, he said that i have to pay maintenance amount from March 2012. BUt my point is since i was not living here and it was not even in my possession, why am i liable to pay the amount. As i spoke to the builder he said it is not my headache, you handle it yourself. What should i do against the builder and am i liable to pay the amount?