You may be in a hurry to find a job, but the black intermediary took advantage of your psychology and promised to introduce you to the work unit after paying the agency fee. But once you pay the agency fee, you will drag your feet, find various reasons to prevaricate you and refuse to arrange a job. Even if you are given a job, the receiving unit will find some excuses to dismiss you, and so on, and the intermediary and the unit will defraud the agency fee.
To sum up, 700 yuan may not get his money back. I hope you will never go to a black intermediary in the future, but you must go to a formal intermediary to find a job. There will be a qualification certificate issued by the labor bureau on the wall.