There is a 7/11 close to nostalgia around 2min walk buy a SIM card comes with internet data and local calls and txt pretty good.
I got away with my own phone using Hotels excellent wifi plus free wifi on all Big Red Bus tours as well as most places you visit. We were in Singapore for 4 nights and had no problems using the normal wifi communications
It doesn't come with a mobile phone. if you have your own mobile phone, you can buy the SIM card at the airport after immigration and use it while you are in Singapore.
Get an answer from Hotel Nostalgia staff and past guests.