The app won't send me a OTP. It worked on a test, now it doesn't.

I can't use a local SIM card because my phone is on installments and is locked. I also need access to my mobile number and texting.

Am I going to have to buy a 2nd phone just to run the app? I know SIM cards are cheap in SG, But how much will the cheapest smart phone + SIM card cost me and can I buy one after immigration in the airport?

Can I use the token instead or is that for residents only?

Thanks