I have just tried to call a disconnected O2 number from Sipgate and it came up

"the number you have called is not recognised please check the number if you need help call BT Cellnet operator on 100 from your mobile"

Thats weird that lol also it wont let me call my vonage phone or my Three 07877 number is their system outdated or something?

Sipgate's routing is probably not up to date email them with the numbers you can't call and they should sort it out.

Just as well I don't use it for my main phone if I did then in an emergency I might not get through to them i might emails them next time i get the chance