Telephone number 0845 602 1111 08456 021 111 08456021111
To disable text messages to your landline (why, really, would someone class that as useful?) you need to telephone
0800 587 5252 (freephone)
Press 1 (change curfew times)
Press 5 (stop receiving text messages)
Hang up when you get disconnected (after a short message)
It will take up to 20 minutes to activate but it does work.
Text my mobile, I don’t read them either but at least I don’t have to cross the room to pick up the telephone for something I can’t hear anyway.