Pressurising from first party in lieu of recording of telephonic conversation

I live in Delhi and working in Govt. dept.ad my family lives in Bihar. In dec 18 a reln came for my marriage , My family has saw the girl in dec 18. When i went home the girl family has came to see me and approved me. When i asked for a meeting with girl, my family has said that you should came last week . My family has talked for land instead of money. In Feb 19, they had shown various plots to my family , but they has already planned for a plot which is costing less than the rest and fooled my family for other plots that the paper were not proper of rest plot. In march 19 I have told my mother for giving me the cell no of the girl for talking but the girls family has befooled my mother that cell is not allowed in the college hostel of the girl. I was provided the girls number on 30 march 19 and the plot was registered on 1st April 19 in the name fo my mother and the girl . I started talking the girl on call , the girl mentioned that cell was allowed but only talking set . Whenever i talk the girl said nothing except her family and most of the time I have to speak. When i saw the girl I felt that she is not right for me , after that I met some other girl and in 10 days I felt that she is perfect for me . now when the first party knew the situation that I am not ready to accept her they are demanding 30 lakhs in lieu of plot that we take the plot and pay 30 lakhs by saying they have audio recording of the telephonic conversation we had and picture of me with girl when i met the girl