Sales of mobile phones slumped by almost a quarter in the six months to the end of September. Results published by Carphone Warehouse Ireland yesterday show mobile phone sales were down 23 per cent in the period. The firm is also predicting unit sales of mobile phones over the Christmas period will be much lower than last year. Despite the slowdown in mobile sales, Carphone Warehouse Ireland increased its turnover to £13.3 million (€16.89 million), from £10.4 million in the same period last year.