Pakistan Housing And Roads Development Corporation - Chakri Road

A few years back I have seen an ad in one of the newspapers and decided to buy a plot of 2 Kanal in installments. The scheme is on the title and I paid by installments all the amount i.e. 2 lac per Kanal. Once I finished installments a couple of years ago, they started to ask me to pay them for development charges, whereas at the time of booking and receiving money they did not mention however it was mentioned in their ad (I still keep a copy of this). They are asking me to pay another 16 lac as development charges. Please shed some light on this.

Thank you