Add APN (+ Button) Option Missing So my gf and I both have the Xiaomi Mi A2, her works perfectly, but when I tried to setup mine, I realized I had no data connection. 

In order to make it work with my provider, I must configure a new custom APN but for some reason, the button to add a new one is missing. I´ve checked, however, my gf's mobile, despite being apparently the same in every aspect, she has such button.

Then I thought there must be some differences between both devices operating system's version, so I wonder if is there a way to compare both to check what I'm missing in order to have the option that I need?

If not, any way to fix this would be really appreciated. 
Thank you in advance
For some reason, without the SIM card or other cards the plus button to add APN appears, which doesnt when having my own card.

Finally I found an app called MyApp, that after installing, it allowed me to edit the APNs, so now everything works as it should, despite it's a workaround.