Walk-ins are accepted at this location, but I definitely recommend you come with an appointment.
Came here last weekend to ask some questions about opening a new line on my current plan, and they put me on their waitlist. After 25 minutes, and seeing my name on the top for a while, I asked when I would be seen. They informed me that appointments get priority, so if someone comes in, they get served first. So, we made an appointment for a later time that day and left.
I consider myself a patient human, so I'm not upset about the wait times for walking in. I just thought it would've been more considerate to let us know about this policy upfront so walk-ins don't have this idea that they'll be served soon instead of an indeterminate amount of time.