I am on a permanently withheld number and when I wish certain contacts to know I am calling them, I simply prefix their saved number with 1470. This works perfectly when I call them. However, when they call me, the phone does not recognise them (because their incoming number excludes the 1470). My old Panasonic phones worked both ways by ignoring prefixes but I cannot see any way to make my new digital phones work (other than labouriously duplicating entries for each contact). It would be VERY handy to have prefixes detected or even, in this particular case, to have the option within each contact to "Always Show" or "Always Hide" your number and let the phone add the prefix required during dialling.
I have the same issue.
I have contacted BT on 0800 800 151 about this and they will get back to me. I am hoping they will fix this in a future firmware update of the phone. I still have the old Dect phone connected to the router and it handles the prefix fine, so it's an issue with the phone, not the DV line.
Note, when adding prefixed numbers to the contacts list, you shouldn’t add the 'Pause' (holding down the 0 key) between the 1470 prefix and the phone number, like you did with the old Dect phones.
Feedback from BT: this functionality was missed and should be fixed in the future.
Like the OP, I have been adding duplicate numbers (with/without the prefix) for each contact into the phone, and got frustrated after doing about 5 of them! So I searched further and found you can do it via a computer by exporting the contacts list, updating it (using the existing contacts as examples for the correct format) and importing it back again. It's still a pain but a little bit easier than doing it on the phone.