Nokia E71 / E71x
Nokia E71 Keyboard
I've tried changing writing language and phone language, but didn't work.
The one suggestion you could try would be to reflash the firmware on the phone to see if that fixes the language problem. But it is rather extreme because you will loose everything on your phone.
All programs, ringtones, settings, pictures, contacts, etc.. will be wiped off the phone once it is reflashed.
So BACK UP ALL YOUR FILES before you do any kind of firmware flashing. remove any passwords on the phone. unencrypt the phone and/or memory card before you flash.