The twins, who appeared on last year's X Factor, will apparently earn £500,000 to promote the price comparison site and will fly to South Africa next week to shoot the TV commercial.
According to The Sun, the pair will use the money to buy more film and music memorabilia, after previously spending thousands of pounds on Michael Jackson's bed sheets and a suit worn by Britney Spears.
They are said to be planning to bid for Justin Bieber's clothes, which are being auctioned to raise funds for Great Ormond Street Hospital.
John Grimes said: "We're hoping to buy his clothes and dress up like him. The only problem is his feet are a size six-and-a-half and ours are a nine so we can't squeeze into them."
Jedward have already starred in campaigns for Nintendo, Shake 'n' Vac and Rowntree's since finding fame on the singing competition.