I had this exact situation happen. I had a space, then filled it with someone who needed care earlier so I didn't have the space then I terminated and contacted the client again and offered the space. It was a genuine concern for them... parents want consistency. I explained to them honestly that I terminated my relationship with the client. They asked why and I was honest... they showed time and time again that they had little respect for my business. They were also late too many times and it effected the way the business ran. I think it tells people that I don't take lates, and I don't put up with disrespect.... I've terminated before and I'll do it again if I have to.
This is me... take me or leave me.