Well, I had a similar experience once. My DG used magic to control my body during one of my trainings. Turned out it was only because I believed her words that she could control me. As soon as I rejected the fact, though, I regained control. So you have to believe in yourself. Try to think that the collar is worthless, or instead, take it off and smash it into pieces, for all it's worth. After all, dreams are made up of expectations and beliefs.