Forfeiture of 5% booking amount by builder due to non concensus of agreement terms

Sir, I had booked a 1 BHK flat from a Reputed builder in a pre-launch offer in July'16 by paying 5% flat cost upfront. The allotment letter (Single page) had a fine print clause that the prices are subject to change. When I asked for clarification (verbally), I was told that if there are any changes in taxation laws, naturally the prices would change over which I replied that it needs to be so mentioned clearly. However I signed the letter after assurance from Sales staff that there was no way that the prices can he hiked/revised since cost is mentioned in the letter, also reasoning that it was anyway not a stamped agreement. Later I was called to sign a tripartite MoU, for which I asked a draft copy in advance to go through. The same was provided by Financer Bank representative after followup. Upon going through carefully, I noticed an Escalation clause which entitled Builder to escalate the flat cost unconditionally and the Buyer would require to pay without any objection. I objected to this clause and requested removal both in verbal & written communication (E-mail). Later, me & Builder's office exchanged few E-mails on this and upon no resolution, I escalated the matter to senior official and had a meeting over which I was told that he would try to take up with Legal Dept but saw little changes of any correction/modification. In Jan'17, I received a letter from Builder that the 5% amount is forfeited since I had defaulted and failed to execute the agreement. I sent reply that it was clearly not a case of default but non-consensus over unacceptable clause of unconditional escalation. I was replied that it was a last communication from their side and that the amount is forfeited. Later RERA was brought to force and I hear that such a clause cannot be a part of any agreement. Yet there is no response from Builder over the matter. Having known their unethical practices, I'm no more interested to deal with this builder and I want my 5% money refunded. Pls advice suitable action which will enable me do so effectively & in shortest possible time. Also I doubt if this case can be referred to MAHA RERA since the incident has happened before RERA was introduced. Thanks in advance. Ravi