Well thats just daft, not putting a subtitle button on it, here you go this is how to turn them off... (taken from the manual)
You can choose your desired languages for Sound, Subtitles
and Interactive (data) Services (depends on broadcast).
1. Press [MENU], select the SETUP menu and press [OK].
2. Select LANGUAGES and press [OK].
3. Select Subtitles, Data Services or Audio using / .
4. Use / to choose the desired language or Off to
suppress Subtitles.
5. To exit menu press [QUIT].