How do I battle against trainers? 1.2.3 version?

In the 1.8 version it was easy to use the Dex to fight againts trainers you already fought. I’m using 1.2.3 but apparently the game says 1.2.2 so I can’t use the feature to fight online.
It’s more important to me the first thing, I need to fight trainers. If someone knows ho to do it, please tell me. Thank you.

Click DexNav and then click the PokeBall icon. Exit the menu and then the list of trainers comes up.

Thanks =) Should I redownload 1.2.3?