you can't without some ridiculous amount of programming. That's the most asinine design in the history of asterisk. Its ridiculous enough to set up individual trunks for each and every tenant, but to do one for each and every handset defies every aspect of how SIP URI's are designed to work in the first place. If you want a sip proxy, buy a sip proxy. If you want a PBX, buy a PBX. One is a relay device, while the other is a concentrator.

Here as the scenario...

I have 1 business running 2 separate divisions.
they need to be able to transfer calls across the divisions.
However they also need to be able to dial out over separate trunks
as there billing comes from the Trunk provider

what would you suggest is the best way forward?

Zayne Nair
Clear Voice

that does not explain why each and every extension needs a separate trunk. At most you've made a case for 1 trunk per division. In that case I would separate them into 2 tenants and enable 4 digit dialing between them.

Ok, that makes a lot of sense.

In another scenario, a client has 3 extensions.
They need to be able to dial out each with their own separate account, but also need the functionality of the PBX. They each use separate accounts when dialing out for billing purposes, as they run a small BPO centre. They in turn bill their clients based on calls made.

Thanks for your assistance thus far

Zayne
Clear Voice

in your new scenario this is just not practical and rather complicated form a programming standpoint to achieve what you want to do. It involves custom scripts and using the custom tag field. If its simply a matter of accounting wouldn't the CDR data provide ample information as to what calls to charge?

you could simply utilize the account code setting of each extension to separate the calls made or calls received to their direct dial. Is it a matter of markup of cost? or is it more like a law firm where they bill based on time spent?