"Hello, sir!"

Translation: Merhaba, beyefendi!

[jzlcdh]

Do people really mix informal and formal like that? If so when or who with? I never heard it but perhaps I move in different circles.

[Ektoraskan]

Merhaba isn't informal, though? It's suitable for every register.

[drumwhacker]

I think 'selam' is more an informal greeting, doğru?