[cisco-voip] CUBE: Rewriting a response from provider and sending it back to CUCM as a 503?

[Robert Kulagowski]

Right now the plan I have with my provider is their "International
Lite" option, so there are certain parts of the world that I can't
call.

That list of prefixes is large.

Rather than whitelisting / blacklisting, I'd like to send the call to
them and see what happens.

If I send them a call to a destination that isn't in our plan, I get back:

ACK sip:+international-block at 216.27.87.199:5060 SIP/2.0

However, the caller hears an _inband_ "Your call can not be completed;
please check with your service provider...". It's not the Cisco Lady;
it's a Britishy-sounding guy, so I know it's from the upstream. At
this point as far as CUCM is concerned, the call went through, so
that's that. But that's not what I need...

Can I somehow take the response that I got from them
"+international-block" and use that to let the CUBE tell CUCM that the
call didn't go through? If I have a PRI in the trunk group, then if
the SIP provider rejects the call I can use the PRI.

I've asked the provider if their SBC can send back a 503 or something
else "negative" so that CUBE just Does The Right Thing and in the
meantime I'll keep reading about diversion headers and SIP header
rewriting, but if it's not possible then that will be good to know
too.

sip-gw1#sh ver
Cisco IOS Software, 2800 Software (C2800NM-ADVENTERPRISEK9_IVS-M),
Version 15.1(3)T4, RELEASE SOFTWARE (fc1)

Thanks.