call out from my landline to other phones, landline or mobile, appears a " unknown caller", so regular contacts do not know its from me even after trying to create contact on other phones. any help please? thanks
Please see this thread: How to activate Caller ID
however in this instance instead of Caller ID you'll need to select the Call Number Display option instead.
You need the "Calling Number Display" feature turned on for your landline service. You can try and do it yourself (as shown here) but if that does not work you will need to contact Optus directly to have them turn it on for you.