Leaving the bank, I was still asking myself "Why she said Moshi-moshi? What's that mean?" When I took a step from the bank, I finally understood. We Japanese say "Moshi moshi" first when we get a phone call and pick the receiver up. "Moshi" means "Speaking" in Japanese, then "Moshi- moshi" is "Speaking speaking". But in English, you say "Hello" first. Why doesn't a person who can speak English but can't speak Japanese think "Oh I see, Moshi-moshi means hello in Japanese".
It is very natural that a friendly bank clerk say "Moshi-moshi" to a person who looks Japanese came into the office. This must be why the bank clerk said to me "Moshi-moshi".