Hi. What browser are you using? I have never had a popup from Optus offering anything free. Use a different one and see if you get popup or delete internet history/cache. Are you on PC? - probably a local issue if your seeing popups at all.
sound like a scam to me..like one of those..you have won !!!!
No way Optus is giving away free phones.....but you now that. Perhaps clean your history/temp files etc. Use ccleaner, its reliable. If still getting popups (which you should not in Firefox), try malwarebytes.
Thanks for the message, @bobskie. Please be weary of these pop ups as we have detected a lot of new scam sites using Optus branding. If you have any doubts always get in contact with us, so we can verify the legitimacy of these ads.