I recently rang a company in the US. While I was in the queue the taped message informed me that someone would "take your call momentarily". In American English, momentarily has the meaning 'very soon', but it rarely does in British English. I could be pedantic about this, but I was calling on a dedicated number for international callers, and they could be more aware that the odds are that international callers will be accustomed with British English (statistically speaking). Therefore, callers are likely to interpret the message in the same way that I did: that someone would take my call for a brief moment, and then presumably hang up. In British English, momentarily has the meaning 'temporarily' or 'for a brief moment only'.
About the author
Jesse Karjalainen is the author of The Joy of English: 100 conversations about the English Language, Cannibal – the language and history of the discovery of the New World, and Roanoke – the language and history of Early Colonial America.