You are absolutely right. Reboot reset new setting back. LTE was removed by Wind that I used before switching. I am looking for permanent solution. I will contact Samsung and will update.
Thank you again!
Update: You can turn on LTE choosing LTE only in 4g Switcher to get LTE data available but... it will void your voice. It is really ridiculous what Wind has done to my device!
Update1: Maybe the problem was solved and this information will be useful for switchers from Wind network that own Samsung phones.
1 Dial *#2263# (RF Band Selection) from your Phone Dialer. ServiceMode menu should be opened.
2 Choose option Band Selection
3 Choose LTE/WCDMA/GSM option
4 Choose LTE/WCDMA/GSM Auto option
5 Choose More in the right upper corner.
6 Choose Back
7 Choose Back
8 Choose End
Restart the phone. Wait some time and LTE connection should appear.
No problems keeping the settings after a restart on the phone.
Disclaimer: PLEASE BE AWARE THAT ANY INFORMATION YOU MAY FIND IN THIS POST MAY BE INACCURATE, MISLEADING, DANGEROUS FOR YOUR PHONE.
USE THIS INFORMATION AT YOUR OWN RISK
Look on messages 9-11
I have used this app. Unfortunately, you are going to lose all new settings after a reboot and have to apply them again. It is the temporary solution.
Problem: Used the post above to access 4G LTE, but lost ability to send/recieve phone calls
Preface: I recently ported my Samsung Note 4 over to Public Mobile from Wind.
This post was very helpful to me for accessing the 4G LTE network, however, after dialing *#2263# I did not have the option of LTE/WCDMA/GSM. Rather I had to pick two out of the 3. I believe that Telus has all 3 types of networks so choosing only two would be less that ideal.
What I did was set my preference for LTE and that did the trick. However, doing so did not allow me to recieve phone calls (but voicemail runs on LTE so that's how I figured it out).
To solve both the LTE and call issue I re-entered *#2263# and selected Automatic.
This allowed me to call my confused uncle back. When I tried to explain what happened, he was less than interested.
I ported over an unlocked Wind Samsung Galaxy S7 and I had the same issues as most people (stuck at WCDMA/GSM). I downloaded the app "4G LTE Switcher" from the Play Store and put the setting to "LTE/GSM (PRL)" which fixes the problem (so that it can go on 3G if LTE is not available). Setting it to "LTE Only" would kill my signal and put the phone in "Emergency Calls Only" mode.
Hopefully this helps you guys out!
I am glad that things worked out well for you. On a negative note (don't mean to be a debbie downer) I would be cautious about downloading apps such as you described. The reason is that the apps can sometimes have spyware that can for example track your key strokes or track your web browsing history. They can then sell this data to marketers.
As the saying goes, there is no free lunch. The coding to switch networks is relatively simply and should be available in your phone's OS. I am not saying that your app has spyware, but I am saying that you should consider the possibility.