How can I make an appointment? I call and they don't answer, I went personally and if you don't have an appointment they won't let you in, but if they don't answer you how do I do it?

If they answer. But you have to wait patiently. Select the option to make appointments.

call at 7 or 8 am

You must make the appointment online

It depends on what you want the appointment for. They take a while but they respond. If your concern can be resolved by phone, they do. If not your case is evaluated by a senior officer to see if it has a solution. Only if those two people don't find how to help you, do they give you an appointment for an info pass?

You must call customer service, and wait patiently

https://my.uscis.gov/es/appointment/v2