There are several methods to be used, first is baby powder, sprinkle baby powder generously, it will help to loosen the grip of the necklace and gently untie it, second, there is oil, you can use cotton and put it in the oil and rob it in the necklace before untying it, you can also use a safety pin or needle place the pin directly on the center of the knot and gently try to wiggle the knot