Attended external transfers

Hi all.

I’m running Elastix 2.5 with Asterisk 11.25
I have an IAX incoming/outgoing trunks with SIP phones (SPA303).
When making a call or an incoming call, we can transfer calls internally absolutely fine.
They want to be able to make an outgoing (external) call and then do an attended transfer to that call to another external number, but it needs to be an attended call.

Currently they can make an external call and use the xfer button on the sip phone and dial another number.
The second number can answer, but as soon as they press xfer, all lines drop.

I’ve tried dialling an external number, once that has connected, dial another external number and xfer whilst the second number is still ringing. This ringing can be heard on the 1st external number, but again cuts off as soon the second number answers.

asterisk dial options are set to “tr” and asterisk outbound trunk dial options are set to “Tt”.
(this is via unembedding freepbx).

Does anyone have any suggestions of what to try?

Happy to provide logs, if someone could please suggest what verbosity I should set it to.

Thanks in advance :slight_smile:

Has anyone any thoughts? I’ve tried various permutations including blind transfer, but none seem to work.

Happy to hear any theories that I could try.

Kind Regards.

How many simultaneous outbound calls your provider give you?(How many channels do you have)

It’s unlimited simultaneous outbound calls (although we only use around 3 or 4). Our provider has asked us to notify them if we are ever going to exceed 100 simultaneous outbound calls, but we are nowhere near that.

Can you share the sip debug of the asterisk cli when this happens?