smasung galaxy s5 active network mode

Hello to all

I own a Samsung galaxy 5 active I have had problems for years with this phone dropping calls on att. It was always like this.

I just bought a samsung galaxy 5 (verizon) and installed the att sim card, and did the changes I found on youtube, and WOW......2 days....900 miles not 1 dropped phone call.

I have the network set to LTE/GSM/UMTS on the galaxy 5.

on the Active 5, I cannot adjust this. its not even an option. HOW can I get the phone to be able to adj network mode?

Thanks in Advance.