I cannot say whether the E is really responsible for the fact that you can no longer make phone calls but receive text messages. But the fact is that the E stands for EDGE - an ancient technology for data transmission. Why the Passport wants EDGE, I don't know, because you can set it in the settings (as with every Android mobile phone) so that the device always uses the best network. So actually, the status bar at the top should not show an E, but a 4G or an LTE or at least a 3G. Since SMS (in the original form, a new standard is currently being established) are not sent via the data network, you can receive and send SMS even if data traffic is not working. Tip: In the settings, check whether the Passport independently searches for the best network - or whether you have prescribed one for it. Note: Little by little, mobile phone operators are phasing out old transmission technologies - first and foremost Swisscom.