Illegal cancelation by indigo developer

Brothers
I need any expert opinion about my case
I booked an apartment in indigo heights gulberg lahore
Initially i deposit 10% @ booking
After that pay 7 % instalment after that due to some personal issues i ask them to sale my apartment and they ask me not to sell the apartment and if i give them in written i will not sell at least next 6 month they can give me relaxation in payment plan (i've it proof too )
Meanwhile prices jump in that area (i booked @ 13000 sqf current price is 16000-17000 sqf. They ask me for buy back at some premium on wich i agreed this conversation was on phone ) they ask me they will update me ina couple of days .
After that they did't contact me in any sort and send me final & cancelation notice that my aprt is cancelled now and return the file and and they deduct 10% of total amount and get the 7% back
Some friends ask me go to civil court as well consumer court & sue them
So want to know what should i do ?