Open a call-prank edit with keyboard typing to set up the office, then put this greeting next as the answer, and follow it with a shocked sound once the caller realises nobody real is on the line.
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This 52-second clip is a recorded Portuguese secretary greeting in a woman's voice, saying thank you for calling in a calm, formal tone. It feels polite and a little stiff, like a real office answering message, which makes it funny when it answers a friend instead of a business.