The promotion offers a chance to win 10 years' worth of holidays to anywhere in the world, plus 200 European escapes to various cities, including Venice, Barcelona and Lisbon.
The campaign, through roster agency Billington Cartmell, includes text messaging, direct marketing, Vodafone retail outlets, channel partners and TopUp retail partners.
Anyone who buys a new phone, upgrades, buys TopUp vouchers or texts or calls from abroad is automatically entered.
Kevin McCarthy, Billington Cartmell's direct marketing account manager for Vodafone, said: "Existing customers tend to leave their phones at home and use phone cards or call from the hotel when they are abroad.
"There's a misconception that it's a lot cheaper than using a mobile. Vodafone now have a flat rate 'roaming' agreement across Europe and the message is that it's just as economical to use your mobile phone when you're abroad."
The UK promotion, which runs through August until September 15, is part of a multimillion-pound global marketing campaign.
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