In message of Sat, 23 Dec 2006, writes
>You are correct in stating that providers such as Sipgate offer a
>"free" number when you sign up with them, but that number can only
>be terminated at your Sipgate account, not any other, so it means you
>have to remain with a Sipgate account in order to keep the same number,
>basically, leave sipgate and leave the number.
>
>With the service we offer, you're able to choose which provider you
>wish to use, and you can terminate the number to any VoIP Destination,
>thus not tied to one provider in order to keep the inbound number. So
>for example if you have a "free" number from the likes of Sipgate
>or any other provider, if that ITSP goes down you would be unable to
>receive any inbound calls on your PSTN number.
>
>Example: You have a "free" SIP account and PSTN number from
>"Snake Oil VoIP" and that ITSP goes down, you'd not be able to
>receive any calls on your inbound PSTN number because the provider is
>down. But if you had a number from us that was terminating at your sip
>address with "Snake Oil VoIP" you are able to login at our control
>panel and change the destination instantly (as changes are real time)
>of the number to another VoIP account to ensure your able to receive
>calls.
>

And what happens when you go under?

No different form any other supplier as I see it.

DF