Network mode not on a preferred setting but don't have choices to change network

[MonikaToney]

When my phone does the device health check, it tells me that there is a connectivity issue. When I click it I get a screen that tells me "your phone could be on a better network. your phone can't automatically switch to a faster network if it's available. You're better off in lte/cdma or global modes for better signal strength.". When I click the button at the bottom that says "see settings", it just takes me to the general settings page, rather than the relevant page for changing the setting. 

I've looked at the network settings and don't see anywhere I can adjust the network mode.