I have a Lumia 950XL dual sim phone (unlocked, USA) with one personal AT&T sim and one work provided AT&T sim. Up until today the phone has worked with both sims.
I could receive texts or phone calls through either number without having to do anything. The phone was purchased new from Microsoft in January 2016 and has worked fine since then, till today January 2nd 2017. Now only one sim card is connected to the network at a time. After extensive time on the phone with AT&T support personnel I am told that my phone is faulty and to call Microsoft.
I can manually select which line will have service simply by choosing which sim provides cellular data. AT&T has made some sort of change to their service which disallows me the use of both sims.
Review about: Att Mobile Phone Service.
Reason of review: Poor customer service.