Pvt Housing Schemes Demanding Ill Legal Development Charges

Five years ago, I buy a plot in a housing scheme near New Airport. In the payment schedule it was clearly mentioned that the cost of plot includes development charges but now the scheme authority is asking for more money which is 20% of the cost of plot. Housing scheme authority says due to inflation they have got special permission from RDA. Can you tell me is there any rule for asking more development charges by society at anytime. In the payment schedule it was shown that cost of plot includes development charges. What should I do? Now I think this society is a fraud.

Imran Salim, please can you name the society?

The name of suspicious society is university town