I'm on a different phone and carrier but I have experienced possibly similar issues - I will make a call, and my phone will switch back to the internal speaker and they can't hear me talk at all. I have to switch back manually to the QC35ii on my phone - sometimes two or three time before they can hear me. I have an iphone 7+ and use AT&T as my carrier. It used to happen just with my Revolves. Now it is also happening on my QC35ii. Obviously one side or the other or both are not talking properly via the bluetooth protocol. Not sure who needs to change (or both) their software/firmware.