Cancellation of sale authority wording

Can anyone tell me how to word a cancellation of authority to give to real estate agents who have brought only 3 people through in 4 weeks. 3 Bedrooms, 2 stunning bathrooms, 2 living areas, studio in garden setting. House is immaculate.
I would rather 3 people who are in a position to buy than 100 tyre kickers.

Even so, in Melbourne you should have a whole lot more than 3 interested parties by now. :( Is the agent fulfilling their contracted duties? Have you commited to inspection times? Discussed your concerns with the agent?

Good luck anyhow....