BT Call Guardian suddenly challenging 'Allowed' numbers.

[#1]

I've had a BT8600 cordless phone for many years, working faultlessly until a few days ago when it challenged a close relative whose number was in the phone's directory and thus an "Allowed" number. Then I discovered it did the same to my own mobile number too.

After some Internet searches - one of which blamed the ADSL filter (not that), I tried various things. First, I tried adding myself as an 'Allowed number', and it wouldn't let me - it was already allowed (being in the phone's directory). So I deleted myself and added myself back - still the same, I got the challenge.

Then having a devious brain, I deleted myself from the directory and added my number to the allowed list. It took it and the phone rang - displaying the mobile number (but of course it didn't know it was "Me", I wasn't in the directory at this point).

This was encouraging. I then added myself back to the directory and it worked as it should, ringing straight away without the challenge and displaying "Me".

The same procedure worked for my relative.

I hope this helps someone - from my research, it appears to be a not uncommon fault.

[#2]

Best guess is that, for some reason, the "presented" number changed (from say 0789 xxxxxxx to +44 789 xxxxxxx) and thus was seen as different.

I've had this with remembered mobile numbers in my mobile phone.

Porting to a different network or even an equipment update by an existing network might cause this.

[#3]

Thank you for responding.

I understand what you mean, and it's entirely plausible - but in this case I'm not convinced it is the explanation, because almost always (as far as I can remember) I had entered the contact into the phone book and relied on that to make it "allowed". The difference was, having cleared out the allowed list and the phone book, I put the number into the allowed list (which allowed the call through unchallenged), then manually entered name and number into the phone book (which changed the display from a number to a name).  My analysis is the software in the base got corrupted and lost the link between phone book and allowed list for at least three contacts - so I assumed it was universal and re-entered all.