our trainer told us to use one command for come. She happens to like "front" as she says, we use "come" to often such as - come here, come on and so forth. Always treat when she comes to you.
The other thing that we were taught was, if they are being stubborn, touch your eyes to make sure they are looking at you and then say come. Nothing else. You may wait a few moments but they eventually learn you are dominant and will follow your command. Do not keep saying "come" or "front" or whatever over and over as this will teach them it's okay to hear several times before listening to you. Hot Rod and I have had our staring contests in the hallway but I always win out.
Good luck.