Shortcut to switch off and on individual cellular network
With iOS - you can automate enabling airplane mode with Siri. Have you tested if you can say ‘Hey Siri - turn off AirPlane Mode”

Automation options in general are:


Siri is the easiest if Apple has programmed that interface and operation
Next easiest if third party / first party automation like Shortcuts and Toolbox Pro apps.
Least easy is assistive touch and voice over. These have a learning curve and you may find it faster to perform a manual step - but they do automate powerfully by non-touch events or not traditional touch events.


As for the other part - how do you have Network Selection in your settings app and how do you accomplish the steps above manually? Putting down step by step might let someone who knows how to automate things help you without needing to see your phone or establish two service accounts.