I would speak with a lawyer, given what you have described you may have a case for various beaches -- an oral agreement is a form of contract, power of attorney

I would speak with a lawyer, given what you have described you may have a case for various beaches -- an oral agreement is a form of contract, power of attorney has certain obligations that are required to be held (the agent has a fiduciary responsibility to act for the benefit of and in the best interest of the principal), and there could perhaps even provable fraud.