Finally had a flight where it was available. I took a 739 continental US and T-Mo worked perfectly on my iPhone (I had some 737 flights over water and no Internet). Just put in my number and started to work. I could not figure out how to use on my laptop instead. It said I could not switch as I was not logged in and was using guest WiFi. Do I need to log into my MP account first on the phone and then switch?