It's not a trick. You need to re-read your listing contract.
If you had a problem with this agent - you should have complained to the agency owner, then if nothing was done, gone further up to the State Real Estate Board.
Good luck working things out
I can only refer you to your listing contract. Most listing agreements are for a minimum of three months, some are much longer. If you were under exclusive contract with this brokerage, you are liable for the commissions regardless of where the buyer came from. IF the contract was in effect
Since this has become a legal issue I would recommend you speak with a lawyer at this point.
if he claims and can proves that the new buyer you found, signed a purchase and sale agreement, is prior to you ending of the contract with him then he has a point.
It is unfortunate your Agent did not deliver on his promises. You certainly have the right to file a complaint with your local Real Estate Board and his Managing Broker. Did you authorize Dual Agency, allowing him to represent both the Buyer and Seller? Who brought in the offer from the Agent's alleged friend?
Your Attorney can best advise you on how to proceed.
Best of luck,
David Jaffe-SRES, CDPE
It's unfortunate that you've had a bad experience with him, but the laws are built to protect both the agent and the consumer. I plow anywhere from $1,500-$3,000 into marketing my listings, so when I sign up with a seller, I am committing to them just as much as they are committing to me.
My suggestion would be to call his broker and talk it over, and/or call a real estate attorney.