Typically a US work visa dictates that you must work for the same employer for the duration of your visa. If you wish to switch jobs to work for another employer or company within the same visa category, contact a qualified immigration attorney who can help you navigate your options. If you wish to switch to a job in a new visa category, you will typically have to re-apply for the visa in order to stay in the United States. This is because different types of visas may have different requirements for eligibility. You must apply and be approved for your new visa before your current visa expires to avoid being in the United States illegally.