Cyan148 Please check again now just to be sure. The option to change the language wasn't present until relatively recently.
If you can't change the language at all, that means you have the English-only version, which in turn is tied to your region. So creating a new account in the same region would still give you this version. But Steam offers the global version, if you're willing to switch over. You'd link your Steam and EA accounts, uninstall Sims 4 through the EA App, install it through Steam, and then download your packs (but NOT a second copy of the base game) through the EA App, under Sims 4 > Manage > View properties. The downside is you'd need to run both apps while playing.