Australian 1300, 1800 and 13 numbers are for incoming calls. You cannot display your 1300 or 1800 as outbound caller ID when calling customers back from CrazyPhone, a SIP trunk, Hybrid SIP trunk or CrazyPBX. Use an eligible geographic or mobile number for outbound calls.
Why can I not show my 1300 or 1800?
ACMA's calling line identification (CLI) rules prohibit using freephone and local-rate numbers for CLI overstamping. Buying, owning, porting or verifying a 1300, 1800 or 13 number does not make it eligible for outbound caller ID. Caller ID Passthrough, SIP headers, a PBX or another app cannot override this restriction.
What number can I use for callbacks?
Keep your 1300 or 1800 for incoming calls, including calls routed through an IVR to your app. For outbound callbacks, use an eligible Australian geographic number (02, 03, 07 or 08) or Australian mobile or Virtual Mobile Number (04), owned on your account or verified as applicable.
Your signup mobile is already registered as a verified caller ID. External-carrier screening can still affect calls presenting that mobile; an eligible Crazytel geographic or mobile number is an alternative. A 1300 or 1800 is never that alternative.
Outbound caller ID is set on the SIP trunk, Hybrid SIP trunk or CrazyPBX extension making the call. Porting your inbound number does not automatically change that setting.
Does this stop me calling 1300 or 1800 numbers?
No. The restriction concerns the number displayed as the caller, not the number you dial. It also does not prevent receiving calls on your 1300 or 1800.
Source
See ACMA: Caller ID scams, under CLI overstamping.