How do I hide my Global SIM number

I have good old Nokia 6230 [which is unlocked] that I use when abroad with mu Global SIM card. How do I set the phone so that my number is hidden?

When I attempt Call Divert to Answer Phone on the phone the request is refused.

On the phone settings there is an option to divert To Another Number - should I be typing in the Global SIM card number at this point?

Thank you for help.