The agency, which has experience of the mobile category through its former client O2, picked up the account without a pitch. It is expected to work on Vodafone VIP, which rewards customers with tickets to sporting, music and fashion events.
The win goes some way to making up for AIS's loss in November last year of the O2 account, which moved to Lida.
The loyalty marketing review was overseen by Vodafone's director of brand marketing, Danielle Crook.
In the past, Vodafone has focused on promoting the VIP programme through retail advertising, which is handled by The Marketing Store.
It will now aim to reposition the scheme predominately through digital activity in the run-up to Christmas.
G2 Joshua continues to handle the rest of Vodafone's direct marketing business, while Rainey Kelly Campbell Roalfe/Y&R oversees its advertising work.
Last month, Vodafone UK called a review of its estimated £10 million digital advertising operations.Follow @SaraKimberley