Where dose the conversation happen?

M: Good morning, I want to send the letter to South Africa by air mail. And how many stamps do I need?
W: Let me weight it for you, sir. Oh, it’s 20 gram, and 20 cents per gram, that is 4 dollars in total. And you could also get express delivery. It is 50 cents per gram, but it will only take about 3 days.
M: It’s too expensive. I will take the air mail and here is 5 dollars. But how long will this letter get there?
W: About a week.