O2 already has a number of deals in place that allow its customers to buy digital wares and charge the cost straight to their phone bill. It now has a new partner in Apple, as the carrier's "Charge to Mobile" program has been expanded to include iTunes vouchers this week. Direct-carrier billing is supposed to be about convenience, but O2 contract and pay-as-you-go customers need to jump through a few hoops to take advantage of this new way to pay. It's handled through an O2 subsite -- o2vouchers.co.uk -- where you select an iTunes voucher of up to £30 that'll be emailed to you when the payment goes through. You then volunteer your mobile number, and you'll be sent a text you must reply to in order to approve the transaction. When the code eventually hits your inbox, you can use the credit in iTunes, iBooks and the iOS/Mac App Stores. A slightly more convoluted process than you were hoping for, we imagine, but at least you can get a fiver off a £25 voucher from now until this introductory promotion closes at the end of next week.