What to do if the builder is delaying the possession

Hi, I've signed Agreement between ATS Casa Espana (RERA Registered) on October 17th, 2015 states that the completion of the said apartment will be completed by December 2017, if failed to do so the builder ATS (per clause Buyer agreement clause 6.2) in the agreement says the company will bear Rs. 5 per square feet per month till the date of completion which is 2-3 percent of the total deposited amount so far. It is a 25 Floors apartment and till date its only on the 6th floor and we are paying as per the construction linked plan. Also It came to my notice today that we will be given possession of the said flat in December 2020. Just wanted to know if I can file a complaint under Punjab RERA Act, Section 18 for delay in possession and ask for compensation per prescribed interest where I do not wish to withdraw from the project.