Lack of clarity in communication leading to flashpoints with customer

I had a customer who had two houses. We had finalized 1.5 Lakh for the entire project. His second site did not get completed on time due to delays in interiors. In the end, the customer said that he doesn’t want the second house to be painted now. I had already told him the bifurcation of the payment, that site 1 will be done in 1 Lakh (with discount 90K) and second for Rs 60,000 Lakh as a round-off it was 1.5 Lakh. In the end, when the work was completed the customer paid 1 Lakh which was the original amount before the discount for the two sites. But he said that you did not charge me the amount which you had originally stated was 90K, but I had already told him that if you do only one site then the minimum amount you will have to pay is Rs 1 Lakh. The customer was not ready to understand this and kept saying that you had quoted 90K so now why are you taking 1 Lakh. This is after everything is done and work is completed. He called after 2-3 months to point out that. Even after explaining him, he was not ready to understand.  In the end, he changed his decision to get that painted and he changed his words about the payment and started blaming me for charging extra. So the customer was very angry about this, and in the end, I asked him that what is that you exactly want? The customer said that what you had earlier quoted you take that much and not 1 Lakh, so now you return that 10K. I notified the dealer about this because he was his acquaintance. The dealer had put in a word for the discount and hence I had done it in the first place otherwise I would have not done it. There was a total 20K profit from that site, so in the end, we returned the 10K to the customer.