Research done by Aurora Kendrick James has shown that workers in the UK spend £400m a year on personal calls from their company mobiles. As AKJ is a "telecom expense management specialist", it does of course have all sorts of solutions to stop this happening, but I am of course not going to tell you about them. They do have one valid point, though - firms who allow this sort of thing are potentially breaking tax rules by claiming back the VAT from their whole phone bill. Naughty naughty.
It's an interesting thing really, personal calls from company mobiles. Many companies offer that as a perk, while other take a dim view... what sort are your employers?