1. Your money was withheld without signing an agreement. I wonder if that person is a lawyer. If you are a lawyer, the formal procedure is that you must sign an agency contract with a law firm (you have a copy in your hand) and issue a power of attorney to the lawyer. Pay the agency fee to a law firm (non-lawyer) and receive an official invoice printed by the law firm. If this is not the process, you can ask him to follow this process. Or I suggest you look at that person's lawyer's practicing certificate.
2. If you want to change lawyers, you only need to unilaterally terminate the original agency contract, but your lawyer fees will not be refunded.
3. New commissions must still be carried out according to the procedures mentioned above, and you must pay the lawyer's agency fee in advance.
I hope my answer can help you!