Don't understand u回复：Is it possible that he can do any harm o

what do you mean? if he has no certification, he could not be your lawyer. That is illegal for him to provide legal help! and he could not fill the G28 form. therefore, USCIS will not let him get any information of you! no harm to you at all. However, if he is a true lawyer, you better pay it following the contract, then fill complain to the lawyer associate.