Potty training help

Ok. Here is the deal. David will say he has to pee on the potty if he has his diaper on but if I put him in undies he pees right through and does not care. He goes in the morning, before bed and when we get home from the sitter. But yesterday tried to put him in undies, he wanted nothing to do w it. Also the sitter said he shows no interest at daycare but she also will not help either. Not sure what to say to her. I have tried to talk to her about it and she wont budge. She said oh he will be trained soon but then wont help when he is there. Do you think he is ready or what should I do? Also we are thinking of leaving her if she keeps this up. She also has the tv on constantly another reason. Not just the pt. But it is annoying. Also what should I say to her? I will have dh also once he goes back to work once he is better.