Dealing with your boss saying the phrase “that’s part of the job” or “wear many hats”

When your boss says “that’s part of the job” or “we wear many hats here”. How do you respond without saying “that’s not my job title”? Been working for sometime and seems like the boss leans on me to do more and more without proper pay. I work on commission but when I do these little jobs which no one else can do I lose the opportunity to get clients. Any advice will do and thanks in advance