After a recent presentation of health plans at her company, Julia Brouck joined ABC PPO. The next week she made a visit to a pediatrician in her plan with her son, Arthur, and daughter, Emmy Lou. After seeing the pediatrician, she was told that there was a $5 co-payment for the visits. "I don't understand," Julia said, "I thought all doctor visits were free."

Explain the potential source of this misconception

Please use specific details to support your answer.