If you are receiving operator signals from neighbouring countries when in the coastal areas of Singapore, check that you have disabled your data roaming settings on your device.
Here’s how you can avoid bill shock from unintended roaming charges.
For Android
1. Go to your device Settings and tap on Connections.
2. Tap on Mobile Networks.
3. Disable Data Roaming.
For iOS
1. Go to your device Settings and tap on Mobile Data.