I spoke with a US-based agent yesterday. According to her, during US business hours, the phone still could be picked up by agents in "Global Call Center". Depending on who is available.

Previously, when I called Taiwan EVA number, all transactions were calculated in TWD. Then converted to USD to my US-issued credit card. I am not sure in this 24/7 system, if charged with USD or TWD is based on who (US or Taiwan) picks up the phone?

I know on United, India-based agents can conduct transactions in US dollars. Maybe for EVA, customer can pick up a currency just like their in-flight duty-free purchases.