Here are some of my ways to control them
1. Get them sit apart. If far enough, they cant reach and talk to their peers. Or
2. Sit in circle or a half circle. In this way, they all turn to you. At least it can minimize their chance to talk. Or
3. To stop somebody talking, look at him or her and ask some unplanned questions about the lessons. It is good that u ask something about the lesson instead of asking them to shut their mouths because they will take time and try to answer you. The rest of the class will be nervous and quiet as they can expect that the next answerers will be them!!!