"Hi! I've heard a lot about your training and I wanted to see if you could help me and my dog. We've been training for a while and, while I like my trainer, I don't think we are getting anywhere. Looking forward to working with you!"
Surprisingly, this type of message from a prospective client is not all that rare. Now, I'm not saying that to toot my own horn. I'm saying it because there appears to be a lack of communication between trainers or instructors and their clients which causes the latter to seek out help elsewhere.