I updated my Samsung Galaxy S6 on August 27. After I did that, I've been unable to use WiFi calling. Due to the build of my apartment complex, I get 0-1 bars i my apartment. I normally use WiFi calling by putting my phone on airplane mode or disabling the mobile network. Now, I get a message saying that my phone was unable to make the call either because it was in airplane mode or there was no mobile network. Every time I've done this I've been able to receive email/Whatsapp/Facebook, so I know it's not my internet. I've done soft reboots and safe mode and every other diagnostic I can think of. The only thing that's changed was this new software update.