I believe this is a SCAM operated by Filipinos using Singapore Telecom Switchboard.
It's a "Telephone Reverse Charge Call Scam".
They call you "pushing a US$10,000 investment product", and ask you all kind of nonsense - "questionaire".
The unsuspecting person on the phone line, either cooperate or don't.
It ends with a bill worth US$25 for the entire questionaire, and US$0.60 if you don't do their quiz.
I believe YOU WILL LOOK into the matter, as it uses a Singapore Telco base.