The ETravelSim Vietnam eSIM is data-only. There are no incoming calls, no SMS, and no Vietnamese phone number assigned. Use WhatsApp, FaceTime, iMessage, or Zalo (Vietnam's most popular messaging app) over the data connection. Most hotels, tour operators, and Grab drivers in Vietnam reach you on Zalo or WhatsApp. Keep your home SIM active in your phone for calls to your usual number and to receive banking OTPs, with cellular data turned off on that line.