How can I go about suing a bank for a loan modification I did not consent to?

My ex husband was awarded the marital home in our divorce with the agreement that he would refinance the mortgage in order to remove my name from it with in 5 years. As the time drew near, he could not refinance and sought to enter into a loan modification agreement. I refused to agree as it would not remove my name from the mortgage, and having this loan on my credit is a huge barrier for me to move on. He has missed payments which hurt my credit score, and the debt skews my debt to income ratio thus limiting my ability to borrow and purchase a home of my own. I had an attorney who advised me to quit claim my interest in the home to my ex so that he could execute the loan modification in his name only, which the bank agreed to. Here I am a whole year later fighting with the bank as they indeed modified the loan, with only his signature yet refuse to remove my name from it. How can it be that a bank can modify a loan with my name on it, without my signature/consent?? I have multiple calls into this bank, copies of the modification without my signature, they have admitted wrong doing, yet still refuse to remedy the situation.