Yes, you can go to an Apple Store without an appointment. If you are going there for service, in most cases they will tell you all slots are taken for the day and make an appointment for you at some point in the future.
Can you talk to an Apple representative?
Apple's main customer support phone number is 1-800-275-2273 in the US. You can also contact Apple Support using the Support website, the Support app, or by going to an Apple Store.