Herman expressed precisely :
[color=blue][color=green]
>>
>> On a Linksys / Sipura device:
>>
>> Use AuthID: yes
>> Auth ID: Your Username
>> User ID: Your verified phone number[/color]
>
> Yes I was trying to use the equivalent on a Fritzbox (Auth ID is called
> Internet Number). Selected "use internet number for registration", and tried
> to call my mobile - didn't work. However, it did work when I called my
> voip.co.uk number. I think it may work on calls to landline numbers but not
> to mobiles. I haven't got a BT/cable landline to check my theory.[/color]

......are you using voipcheap.com....?

WRT presentation number to mobiles - are you testing with Vodafone, by
any chance?