You'll always be sure of what you are getting by reading the label.
If "whole wheat flour" is not the first ingredient, you are not getting a whole grain bread.
In fact, if the second ingredient is "unbleached wheat flour," you are not getting as many whole grains as you could. The ideal whole wheat bread should have one kind of flour -- whole wheat.
If your question is in reference to breads "made with whole grains" (or those labeled "multigrain"), then you have every reason to be suspicious, since they are not whole grain breads.