Just say your Sim has a medical career and has the position of Paramedic. If a problem comes up while they are at work and you make the wrong decision, they may get demoted. To get their position of Paramedic back,go on the computer and search for a job. (By the way, I have only done this ONCE) During the search, an offer will come up for a Paramedic position in the Medical career. Accept the offer and your Sim will have their job back!