Weak 4G/LTE signal

[amirhossein1]

It hqs full bar on 2G/3G but when i change it to the 4G, first it is not stable , whenever i want to call or send message it will take long time,
They other way that i tried was i changed it on 4G only from *#*#4636#*#*
But i cant call or send any messages ,
sony z3 doesn't support VOLTE !?
Or it doesn't have any sitting to fix it ?

[amirhossein1]

Ok,
could you help me to prove my 4G signal ?!
it's very weak,
I don't have stable Internet speed on my data,
Is there anyway to fix it?
Does ram dump help to prove the speed !