Can I edit the APN code when it only provides default options?

[AC Question]

I am trying to edit the APN code on a Kyocero Hydro Air, it forces me to only choose from specific codes.

 

[Guytronic]

Usually you won't be able to change established fields in the existing APN settings screen.
If there is any option to set an alternate APN as a new entry and then save it as a new default that might be your problem.