A good friend of mine gave me a tip for dealing with kids and the natural law that moves them to need you as soon as you get on the telephone.
She trains her three children to squeeze her free hand or to squeeze the arm she's not using while she's on the telephone. This is a silent signal between the two of them that they need her. They continue to stand next to her quietly until she has a chance to ask the person she is talking to for a break.
I've been on the phone with this lady several times and I rarely ever hear her kids in the background. But, without fail, she will have to ask me, "Will you hold on for a second?" and I am always surprised to hear one of her children standing right by the phone who I didn't even know was in the same room with her.