Delay in Flat payment

Hi, I have booked a 2bhk flat of 42.41k. while booking I only paid booking amount 50k. I wanted a ready possession flat but since my own contribution was in FD and it was getting matured in June so I booked this flat as the executive told me that it will be ready by July. He didn't give in written because he was saying due to new government rule, we will be keeping one month buffer so in agreement the date of possession will be Dec 2019. But he was giving this assurance to everyone who was coming with me to visit the flat.Hence, we booked the flat and we confirmed that we will make the payment by July. Now the issue is, they are saying that they will give the flat by December and they want 85% amount by July. I spoke to the director, we had arguments but somewhere we said OK because they were saying if you can't afford you can cancel the flat we will return the whole amount. So we adjusted and said okay we will give you 85% of the amount by July. But due to some time constraint own contribution extended one extra week. So after making the payment, on Thursday, they called me and said we will send you the demand letter and receipt of the payment on the email. and we will keep the documents ready so that you can complete the formalities on Saturday smoothly. I said okay first send me the receipt we will proceed on Saturday because I will not be available on Friday. Here bank is open on Saturday and Sunday so we could have done that. I had a meeting on Friday morning. Mobile phone was not accessible not even personal mail. They kept on calling me since morning 8am, but I could not reply. Then send a message that you need to forward an email to bank with the documents we have attached. I somewhere got agreed that fine I will send it from my mobile, but there was a consent letter which needs to be signed and attach which was not possible. I told them that this letter is there, which I can't proceed, they said it needs to be done by today else you have to pay the interest because Sat Sun and Monday bank will be closed. I spoke to the Bank agent with whom I had done the loan procedure, he said that bank is open. Now the executive doesn't have anything to say. So I sent them an email stating that i was ready to forward the email with the docs but since there was one doc with signature, and I was not able to access the system, so I mentioned that I was not intimated earlier, therefore I will send by evening. So replied on the email that, we did try to call you but you were not responding. As per the commitment, please give us the disbursement by 30th Jul else you will be charged 12,701rps per month. which was not intimated me earlier. So what should I do now? i am frustrated with ths