It sounds like you've lost them and lost control. My advice would be to keep it very simple. Don't try to teach them anything to start. Look for an activity that gets them excited and catches their attention. Just have fun, get their trust, and then try to get them to speak a little.
You may have to take the class down to the gym and play dodgeball. Once you have the students engaged, try to get them to answer a question before they throw a ball. You'd think they wouldn't do it, but if you tell them that if they don't ask the question, the person on the other team doesn't have to sit out, THEN they will.
Slowly, you can stop that kind of activity as you gain their trust and essentially control. Then you can bring them back to the classroom and regular teaching (with the promise of heading back to the gym, if they're good
)
How many students do you have at a time? Are you teaching within a curriculum you have to finish?