Builder asking for extra payment post sale agreement

Hi All, I bought a plot from a reputed builder detail as follows: On Aug 2021: I paid 3 lakhs to book the property. On April 2022: I paid 5.5 lakhs to get my sale agreement done. April 21st: I finished my all loan procedures including POA and left abroad on April 22nd. After which, the loan was rejected due to the KATHA issue because my plot didn't have an individual Katha. Post which, I continuously followed up with the builder team regarding the release order and the registration. However, the builder representatives asked me to wait which took 2 years 6months to get the release order of the plot from the date of sale agreement. During this period, my father has visited the branch asking for an update. I have personally contacted them multiple times via phone. They stated " Sir, we are awaiting your release order of Katha and nothing to worry". However, during this time period, they have also emailed me stating that, my property development is 30% completed on June 2023 and 70% completed on February 2024 and asked me to proceed with the remaining payment. I didn't respond to them via email but I contacted them through phone and they assured me not to worry about the Katha release and plot safety. On 30th August, They sent me an email, stating that they have received the release order for the plot and asked me to proceed with the loan process. I started my loan process on the 2nd of Sep 2024 and on 3rd of October I got my loan approved. However, the loan amount was not dispersed yet because my POA was not done due to the delay in bank end. Finally on 12th of November, when I contacted bank, they suggested me regarding the POA which I completed on 27th November 2024. On 12th November: I received an email from the builder that they received the Katha and asked me to do the registration. Because of my POA, I was unable to do the registration but the builder representatives were completely aware of my entire situation and they also agreed to wait for the loan process to complete which was completed on 27th November. On 6th December: I got an email from the builder that my registration deadline has passed and asked me to come forward for the registration but I didn't respond to that email because on the 5th I spoke with the builder and bank representative already and they assured that they will process the amount soon to the builders. On 10th Dec: I got an email from Builder again stating that my allocated plot is cancelled and they are demanding me to pay extra 2000rs per square feet. Could someone please suggest me what can I do now? I am not agreed with the new payment and I am planning to proceed legally. What is the best advice and suggestions in this case. Please suggest.