Khayban e Amin - Incorrect plot size

We bought corner 10 marla plot and paid (65 lak) which was given (21 22 lak) few years back by society. But the plot is of 8.5 marla size and now they are not giving us remaining 1.5 marla or the money. Since day 1 the society knew the size of plot but they in paper mentioned incorrect size. We are very upset as it was our whole life saving and its a loss of 10 to 15 lakh... Also we bought plot for growing family size and now the size of plot is smaller. Should we sale the plot in low price?
Or go to courts? What experts suggest?

@shabir sb

salam

never buy a plot in marla's, buy in sizes feet like 3060, 3570, 4080 and 5090.

because there are a huge difference sft in marla.

1 marla = 250 or 225 sft in Islamabad , lahore

1 marls = 272 all pakistan