Up to 28,000 consumers who were mis-sold Carphone Warehouse’s Geek Squad mobile insurance and technical advice service could be due refunds after the company was fined £29.1m by the Financial Conduct Authority.

The FCA said this week that Carphone Warehouse failed to give its sales consultants the correct training to enable them to offer suitable advice to customers buying the product, which tended to cost about £5 a month. They were trained to recommend it to customers, many of whom already had cover through their home insurance or bank accounts, it said.

Between 1 December 2008 and 30 June 2015, Carphone Warehouse sold Geek Squad policies worth more than £444.7m, a large proportion of which were later cancelled. The watchdog carried out an investigation after whistleblowers raised an alert.

While the fine will be paid to the Treasury, Carphone Warehouse has set up a redress scheme, with £2.3m to compensate affected customers. Contact the firm by phone on 0800 049 6190 or go to Geeksquad.co.uk/contact/complaints.