Haha. I agree with Glenn. I think the person meant "What if the SELLER.... can the SELLER cancel..."
Typically no unless that was put into the contract as a clause. That said, if the agent hasn't done a whole lot of work, they'll likely agree to let you out of the contract. The potential for bad publicity would probably outweigh their need for that contract. If they agent says no, maybe go above their head at the firm. Also, you could potentially be difficult and wait out the contract, ie "we decided we want double the price." They can't force you to sell it even with a contract. But, they can force you to pay them their commission even if you sell it yourself or use a different agent. I'd suggest speaking to the agent in a calm manner. Most people are very reasonable when approached properly.
If the agent does have a whole lot of work into it and you're confident it wasn't a bait and switch (they actually DID have a buyer they were confident in and didn't just say so), then why not give them a chance?
how about reading the questions for errors before you post.
I think some of those words should be changed to "seller" shouldn't they?