Xperia xz premium 4g network very slow to start working

[Alias797]

So my Sony Xperia XZ premium is really slow to start 4G network even though 4g signal 📶 is full. I tried to sim card on other phones and this problem disappeared. So it seems my phone doesn't want to work as it should. It's happening work long time now, I thought it will disappear after updates but it didn't. So please help me, because when you need Internet and the signal 📶 is full in 4g, but my phone not finding Internet 

[AvalonFR]

I have the exact same problem, Xperia XZ premium red limited edition (bought in March 2018) I am starting to regret my decision, my Z5 had better network connectivity.

Please do something ASAP

[PDas]

Sometimes me too find the same problem, but one trick helped me to resolve as dialing *#*#4636#*#* to go to Phone Info>Set pref network type>drop down to select LTE only.

And sometimes this also makes problem, then I switch it to LTE(preferred)/WCDMA/GSM from Settings>Network & Internet>Mobile Network>Preferred network type.

Please apply this trick and let me know.