Option to select network mode not available
I have an LG Phoenix 4, unlocked, and am using SpeedTalk for my carrier. SpeedTalk tells me that to resolve an issue with cell service intermittently failing until I restart, I need to switch my network mode from LTE to 3G/4G. However, no network mode option is available under the Mobile Networks option. What might I need to do to access the option to configure the network mode?