Runwal Group — Late possession

Address:

Lenyadri apartment kisan nager no 3 thane 400604

I have booked flate in runwal mycity dombivli manpada road .in 2018 .now allmost 6 years completed and in agreement possession date is december.but i couldn't get possession till now as I suffer lot .they told me on December pay full payment.as i paid full amount in December but they r not giving possession.and now no one is answering any thing about possession.i don't know what to do.