You can contact your passenger by call or message. Don't worry; the passenger can't see your mobile number due to number masking.
Call the passenger
If there's no Internet connection (either you or the passenger), the call will route through your regular telco. You will see a virtual number starting with +65 31XXXXXX (a masked number). Tap the call button to proceed with the call.
Message the passenger
You can also send a short voice note () to your passenger
⚠️ Safety first! Do NOT use your mobile phone while driving.