I have a phone with BT call guardian. Recently BT call guardian kicks in on stored contacts/allowed numbers to make them announced calls. It did this once when I myself tried to phone my home number, but on redialling, it got through. But yesterday it routed a call from my number and at least one other number to call guardian. I have notice that the display on my phone (BT8610) did not light up and display anything at all and on viewing the number which has tried to call, put the call down as "no number". Is this a problem with the phone itself or another issue. Is there a solution? One suggestion from the BT community forum is "
the malfunction you describe is due to a corrupted or missing caller display signal which is sent down the line just before the first ring is sent out.
Corrupted signals can also be caused by faulty broadband filters in the broadband equipment, but in most cases, its due to a line fault which would need to be looked at by Openreach."