Based on my cruise in January this year, there are separate 5Gb data buckets for Mexico and global high speed data I used in Panama and South America. I believe on T-Mobile your plan per line home data is also separate from your roaming data use. In my case, I saw on my app that the monthly total for lines did not add roaming data use to the line total. This hopefully will preserve my $10 line discount a month via Kickback and still allow the full 5Gb of high speed roaming on the same number. I also saw this effect in May of this year. I am going to Europe in October so I will try and wring out the details of this strategy and report the results here for reference.

I have also noticed that iPhones do prompt users to allow WiFi password sharing with other iPhones trying to connect to the same network. No QR code was needed or offered, just a simple yes or no for the guest to connect.