Customers tweet their personal recommendations for BE Broadband via a special Twitter application that includes a link.
Followers who use the link and sign up to the BE Broadband service receive a £20 credit.
The 10 most successful referrers win a year's subscription to DVD and online movie rental service LoveFilm. Success is measured by earning one point per follower signed up, minus one point for any followers who had been already contacted by a different customer.
Chris Stening, managing director of BE Broadband, said: "The ‘Be a Hero’ application is a different approach to the usual referral schemes, encouraging BE members to invite their followers via Twitter before others do, with only the first referrer getting the credit.
"This combination of gaming mechanics, along with the member-get-member referral, will encourage BE members to take up the challenge and spread the word about BE."
Social media have been shown to be the best at driving brand awareness, but many brands have found it difficult to use social media effectively.
The Office of Fair Trading set a precedent for promotional blogging and tweeting in December, when it won a pledge from Handpicked Media to fully disclose their promotional blogs and tweets.