[smeej]

Is it harder to spoof a number in Singapore than in the U.S.?

In the U.S., it's trivially easy to make your call look like it's coming from whatever number you want, so scammers just have caller ID display the real phone number for the bank they're pretending to call from.

[fmajid]

No more, see SHAKEN/STIR:

https://en.wikipedia.org/wiki/STIR/SHAKEN