Galaxy A7 2017 , disconnecting and connecting to the 4.5 g Internet

[mojtabaqri]

The problem is : 

disconnecting and connecting to the 4.5 g Internet ,  when I use sim card data ( internet ) .

Network mode is constantly changing from 4.5 to 4 g and vice versa

Unfortunately, this problem did not exist before the phone update, but it did happen after the phone update

[JagSh002]

I never heard 4.5G. What is it? And from when are you facing this issue?