Not a Minute Before, Not a Minute Later
The one good thing about working in customer service is usually that the work is shift work, which means that you have very specific hours in which you work. So when the clock ticks one minute later, you have no obligation to be there which is great freedom.
Even when your coworkers need help, you technically don’t have an obligation to be there to help them once your shift is over. Whether you stay to help or not is entirely up to you, but more often than not you will probably choose not to.