My question involves real estate located in the State of: CA

My mother & I have just put our home up for short sale a week ago. Our agreement with our agent is that other agents who wish to show the property would respectfully inform us or contact us at least an hour in advance, by appointment only. My mother got into a confrontation with an agent who didn't call but decided to show up anyways as if this was a walk-in invitation. What rights, if any do we have as far as showing the property. Can we refuse if it's not at a convenient time?