CID Not passed on transfer to external numbers

[TalleysAdmin]

We have an issue where our users are transferring calls to external numbers and the system is sending the default SIP trunk phone number and not there extension outbound caller id.

Is there a way to fix this as we plan to have 3 different sites setup, and the Sip trunk default number cannot be used.

 

[leejor]

Does your provider allow you to send a number, other than the default trunk number? Have you reviewed the outbound trunk caller ID options? If a call is placed (not a transfer), does the called party see the extensions DID number, or the default trunk number?

 

[TalleysAdmin]

Yes, the called party sees the DDI setup in the Outbound Caller ID field when a call is made directly.
It seems to only be when blind transfer is used, if we use attended transfer the correct DDI is seen by the called party.

 

[leejor]

I'm wondering if the original callers caller ID, is attempting to be passed, and that is rejected by your provider so the default trunk number is used instead?

 

[TalleysAdmin]

I have run some packet captures on the traffic to the sip provider and have found it is sending the callers DDI.

For example
Message Header

Contact: <sip:[email protected]:5060>
To: "6421xxxxxxx" <sip:[email protected]>;tag=NBUcSDKScvX7g
From: "Paul"<sip:[email protected]:5060;transport=udp>;tag=9d5e3b73

 

[leejor]

So it is sending the caller ID that you want it to? It's just that your provider is then sending the default trunk number to the called party?

If so, then how does this Header compare (differ) to one that is working the way you want it to?

 

[TalleysAdmin]

yes, it's sending the correct caller ID to the provider but the provider is rejecting it due to it not being a trusted outbound number.

This is why it falls back to the SIP trunk default, You can not send other companies CID as your own.

The only difference is you see and extra "ACK" in the packets sent to the provider, the first one shows the number you are trying to send and the second one show the default number being sent.

 

[leejor]

So, in essence, 3CX is treating a blind transfer, in the same manner as a call forward, in that it is sending the originators caller ID, which your provider ignores then uses your "default" number. There are a number of outbound trunk options that specify from where caller ID is taken. You may wish to do some changes, and tests, to see if that will make a difference. Before changing anything, make note of the original settings as some changes can cause all call to fail.