A change on our VoIP platform as meant that we are sending the caller ID in international format, ie, +44... instead of national format (eg 0...) This may be causing some customers problems where they are expecting the CLI in a specific format. This was an unintended change and we're looking to reverse it and put the format back to what it was.
A fix for this is being tested at the moment.
We've put in a temporary work-around to fix the CLI format. We are doing planned upgrades of our call servers which will implement the long term fix. These upgrades will happen over night over the next couple of nights without disrupting the service.