I just got this call and my number is on do not disturbIs it from Optus?

nuisance call

Rob - Contact A Current Affair/Today Tonight, they'd love to investigate and bring the sucker down. Man that'd be funny to see haha

HI GUYS ! I SUGGEST IF YOU WANT TO PREVENT THIS FROM HAPPENING , GO TO THE "DO NOT CALL REGISTER" ON THE AUSTRALIAN GOVERNMENT WEBSITE. JUST ENTER YOUR MOBILE PHONE NUMBER, EVEN YOUR HOME PHONE NUMBER IF YOU WANT. From the time you register your number, it may take up to 30 days for individual telemarketing agencies to recognise your registration, and stop calling to your number. Under the Do Not Call Register Act 2006, telemarketers can check their calling lists against the Do Not Call Register. If a telemarketer calls a number on the Do Not Call Register, they may be in breach of the Act, and may face penalties. ThanksHope that helps.

Just got the call then, hung up though just as they mentioned the question.
How did they get our numbers? and how can this be stopped?

In general, if it is a pre-recorded quiz then hang up straight away because you might be being charged like $5.00 a minute. They want you to continue the connection to rack up the charges. Simple scam.