This is really annoying me: I've got a Philips cordless landline phone, which supports SMS. I'm sure when I first got it I tried text messaging and it worked, but now when I send a message, I get a message back from BT saying the text could not be delivered.

The problem seems to be after entering the message and the number, it asks for an SMS box number (I presume it means on the phone that I am texting), which defaults to 9. Then when I get the error message back from BT, it say the destination number was the phone number I put in, but with a 9 on the end of it. So I tried another text, and this time deleted the last digit of the outgoing phone number, which was a 6, and then put SMS box number 6, and it worked, obviously it put the 6 back on the end of the phone number, but it's an annoying way round the problem.

Has anyone had a problem like this? I don't know what an SMS box number is; is it unique to philips phones or do all phones have them? Also, there seems to be no way of turning off the sms box option, or leaving the SMS box number blank, if I delete it then it just adds a 9 to the end of the number I am texting, thus getting an error message.

I know I'll be lucky if anyone knows how to fix this, but I thought I'd ask. It's driving me mad as it did used to work.

The SMS box number is a sub address which is required on all SMS landline phones.
It enables up to 9 SMS text phones on one fixed line number to receive individual text messages.
The default setting is usually 9, which will also collect any texts without a box number attached, or which have the wrong box number.
It seems the phone number you are sending the text to doesn't have a phone set to the default box 9, but to box 6 instead.
You need to check the box number setting on the receiving SMS phone.
I would also suggest that you type RESET and send it to 00000 to ensure your service is functioning normally.
You should receive a confirmation text in return from BT.