Do you have the it in writing, signed by you and the agent?
Do you have emails confirming it?
Do you have an ad where its advertised?
Some or all of those may work. Call the managing broker.
If that doesn't work, I would go directly to the state real estate board.
Call the real estate board and speak to someone and file a formal complaint .
Calling the broker is always the first step. I can not stress to you enough the importance of having written proof. Your word against your agents is always hard.
Good luck and I'm so sorry this happened to you.
William E Wood& Associates