Good afternoon. So, you made a mistake and tried using good morning after 12 p.m.? Good afternoon is the phrase you should use, and though the line between afternoon and evening is a little blurry, you can use this phrase until 5 p.m. Good evening. Evening generally takes place between 5 p.m. And 10 p.m., some say evening goes right until the moment you fall asleep.
In any case, this phrase is used for that period of time after dinner. Hello / Hi / Hey. Don’t want to be confused about what time of day it is? You can use these phrases.
Hello has the highest formality and should be used for people you don’t know or in formal situations. Hi is slightly less formality, but I wouldn’t use it for people in authority.