Training a sheepdog not to take other dog's commands

I have my 3 dogs with me to check sheep on the mountain today. Sometimes sheep wander a bit and get down into forestry and just need a little touch back up onto their own ground. In the end of this clip I just gather a few sheep because 3 are on the wrong side of a fence and I want to put them with their friends back on the mountain side of it. The sound didn't just come out as well as I wanted on this one