Is it A case of breach of trust

ir ,my father has given money to person on the basis of his land as security in 1998.by the time he repay some money out of it but after his death his son refused to repay the money so there is one time settlement with them for 60000rs. but there is no document for that but we have two "gawah" at the time of settlement.we received only 10000rs. we try to recover remaining but they said they will give it so we gave them time now they refused to repay remaining.now we have 3 things a)contract of 1998 with there deceased father for money given and a land as security b) two "gawah" of one time settlement c) recording of there sons voice for that they owed money but they dont pay.