Amendment in Account and Correspondence by Title Owner

My Ex-wife is a title holder in a property buyer agreement, where in all the payments were done by me approximately 12 lakhs upfrontly and loaned 16.9 lakhs from bank under EMI subvention scheme in 2008. This property is in Sonepat and still not built. I filed a divorce case in May 2011 since then I am living seperately. Recently last week, due to NPA for loan from bank, she was called to bank where we have joint account. IT happened due to non-payment of EMI subvent by builder to the account 4-5 times. A case has been filed under 138 and appearance was called for her to be present in Ludhiana Courts, to avoid that she paid outstanding and now bank is asking for more money. In midst I received wapp msg from my son, and was shocked to read that he wanted property papers (buyer's agreement), which I denied. Now, recently a relative of mine known to her went to builder's registered office and modified the correspondence and savings bank account - joint name to her address and bank account thru my wife's written email. Please let me know what steps can I take to first void all such modification and to protect my interest as I even after paying all money to builder avoid anybody's intereference in it. Regards, PS