Sony XZ1 unable to receive and make calls when in 4G

[Graycells]

Good day everyone! Sony subscriber from the Philippines here.

Please help me. 

About four months ago, I noticed that I was unable to receive and make calls when in 4G.

But if I switched my preferred network type to 3G, the call issue would resolve.

However I need to use 4G for better internet connection.

This inconvenience is also associated with total loss of network connection for few minutes whenever I manually switched network preference from 4G to 3G, to be able to make and receive calls. 

I purchased Sony Xperia XZ1 just fine until recently it become inconvenient to use for me. 

Is there any way to resolve this issue?

Tried already the troubleshoot suggestions from Sony Mobile. 

They also recommend using VoLTE which is not compatible with xz1.

Thank You, Sony subscribers. 

[Aifaasmudge14]

I have the same problem. This morning I had switched into 4G and didnt realized someone cant call me or I cant make outgoing call with it. Search for the solution here and saw your post. So I switched back into 3G and those calls are able now. Wonder why it happened though.

[Jhero]

its because of VoLTE is not available in the Philippines. 

[XZ1-User]

"They also recommend using VoLTE which is not compatible with xz1." - The XZ1 single SIM model firmware includes a lot of modem configuration files need for using VoLTE. Which telecom provider do you use? Vodafone?

[Aifaasmudge14]

I am living in Malaysia and Im using one of the main telco in this country. I dont think it is because of the VoLTE or anything, because it was once perfectly working until that day that I cant receive calls or make any calls..