When can I sign the F4 visa in person?

You can check it by phone in the middle of every month.

Dial12953-001-202-663-1225 and then press the key: 1-0-0 (press the key as long as there is a voice prompt); Then the voice will prompt you to wait for the visa officer to answer the phone. Generally, real people will wait for 3 or 5 minutes (sometimes a little longer) before answering the phone. You have to tell him your visa type and want to know the interview time. He will ask your case number and name, and will tell you when to interview after verification.