Carmen - IF your buyer gets through the entire process for buying this house (negotiating price, signed offer/contract, inspections and re-negotiating after inspections and keeping the contract moving forward with the title work and lending companies) - your new agent will have put in alot of work to work to get a "closed" sale. You may find your realtor is willing to take a reduced fee or you could ask to cancel the exclusive and have your realtor sign a Transaction Broker Agreement instead (which means they are responsible for facilitating the transaction only but not representing to the buyer or the seller) to complete the transaction at a reduced fee. I would stay with the Exclusive with a reduced fee negotiation myself as you might find you need that representation during the negotiating that happens after inspection process
There are several options here - but having a interested buyer doesn't always mean a closed sale. There is a long way to go to get to the closing table. Use your realtors expertise to close the deal and work with him/her to come up with compensation that is fair for everyone.
Good Luck - Joleen
Now if you really want to fight it -- check with an attorney. You MAY have a right of recission on the agreement you signed with the real estate agent.
Another option -- is talk with your agent -- actually, the employing broker. Tell them this was an earlier prospect and show them some proof of contact. Ask them to drop their commission in half as result. This way you can get the benefit of representation at a better price.