Need help rearranging my schedule?

I may have just been hired at Jewel Osco and I don't want to make it seem like I don't care about work because I do, but I have plans this Saturday I've had for a week now. My parents are still trying to argue with me that I need to work and I would of course be grateful that I got a job but these plans are important to me (this job is actually part time). The hiring manager mentioned orientation but she didn't actually tell me that I'm hired, just that I have to call her in the middle of the week. What can I do to make both plans work? 10 points best answer. Thanks.