Mansfield is chief executive of Captial Radio owner GCap Media, the UK's largest commercial radio company. He joined the board of Capital in 1993 and was appointed chief executive in 1997.
Carphone also announced the promotion of chief operating officer for telecoms David Goldie to the board as an executive director.
Deputy chairman David Ross decided to move to a non-executive role to reflect his increasing external commitments.
Meanwhile, the retailer said group revenues, including retail sales and telecoms services, rose 23.3 per cent in the first quarter of the financial year. Retail revenues increased by 17 per cent to£259 million. Like-for-like sales increased by 3 per cent.
Carphone chief executive Charles Dunstone said: 'Progress so far this year has been ahead of our expectations. The mobile market environment continues to benefit our model, and growth in subscription connections has picked up from the fourth quarter.'
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