Simmer chicken in water to an internal temperature of 165°. Remove from water and cool fully.
Dice chicken into ¼ - ½ inch pieces.
Preheat the oven broiler on low and lightly toast the bread.
Combine chicken, celery, onion, mayo, salt & pepper in a bowl and mix thoroughly.
Lay the tomato seasoned with salt and pepper on the bread, layer with lettuce, chicken salad, and cheese. Fold in the ends and roll up. Cut in half and serve with chips and pickles.