I have an iPhone 6 running IOS 10.3.3. I am going to add the $15 Unlimited Text Roaming Plan for my 10 days US trip next week. I do not want to use any Roaming Data and will only use Wifi for data. Questions: 1. Are these the correct settings: Cellular Data - On; Cellular Data Options - Roaming Off. I believe Cellular Data must be on for SMS to work (?) 2. With the above settings, I believe iMessage will not work - because it uses data (or Wifi). Must I also turn iMessage Off to ensure no data roaming charges: my preference would be to leave that setting on so that iMessage continues to work on Wifi connections. Thank you for any help.