I have both iPhone and Android, but it didn't work. Kogan in Australia has a service called  

Kogan in Australia

The Premier Access Bolt-On adds extra services to your active plan, giving you access to international calls, SMS and MMS, as well as video calls. 

When you’re in Australia up to $14.90 worth of the following services are included:

• Standard national and international video calls
• Standard calls, MMS and SMS to international numbers
• Directory Assistance 1223; and
• Call forwarding within Australia
• Premium calls to '1900' numbers

What's not included - All services not listed above, including but not limited to:

• SMS and calls to selected premium numbers
• All national Voice and SMS services
• Any type of Data services
• Calls, SMS, MMS or video calls to non-terrestrial locations such as satellites and space stations;
• International rerouted, freephone, pager and premium numbers
• International voice call diverts or call forwarding;
• Use of the VHA Network that is for a commercial purpose or for resale by you; and
• Calls and SMS to the Pivotel Network

tefo1400:

 

I have both iPhone and Android, but it didn't work. Kogan in Australia has a service called  

 

 Premier Access Bolt-On for call forwarding but in NZ don't have that 

Yeah sounds like they just don't have it built into the plans/locked like our prepay plans.

Kogan's website says it can be done 

Diverting calls to another number is possible, but only via your handset, not the network.

Not all handsets have this functionality, so be sure to check your handset user manual for instructions on enabling this, if applicable.

Interesting.

I just grabbed my fiancees phone who is on Kogan Mobile and when attempting to do always forwarding I get a unexpected response from network.

I'd push for customer service to raise a ticket with us to see why it isn't working when their website says yes.

OneNZ Prepaid subscribers can not use call forwarding (via mobile network) so I would be surprised if Kogan customers can

when I tried on my Samsung s21 ultra it says ( something went wrong. check your sim card or network connection, then try again 

Linux:

 

@MaxineN This is working as designed Prepaid subscribers are not enabled to setup call diverts at network level

 

This is the answer (and also what my assumption was as it's not built into the prepay propositions much like ours).

It's a bit interesting because to my knowledge the only diverts I know of is on the network level via phone settings(as per my first post).