There is smallprint to consider, but the headline is pretty much as it says – buy a phone this month at Carphone Warehouse and you get three months of Napster Mobile.Napster hit the iPhone and Android handsets in the UK back in May, treading much the same ground as Spotify and for much the same price, around £10 per month. When you happen to be in a 3G or Wi-Fi area, you can search and play any of the tracks in the company's catalogue, with the option to save albums, tunes or playlists on your mobile device to play later. You can also sort out playlists online and sync to your phone, as well as being able to access radio stations and pre-made playlists. New releases and current charts are also available instantly too. It's a good service, but perhaps playing catch-up to Spotify right now.Which is perhaps where this offer comes in. It gives you a chance to try it out on your new Android smartphone or iPhone. Once you've got your phone, you'll get a text message with a promo code and link to register. Once you've done that, get the app and away you go. Credit card details are required when you register, so you'll get charged if you forget to stop the service after those three months. Just make sure you're on top of it. Unless you feel it is worth the £10 fee after three months. In that case, carry on.The three months is for pay monthly phones, If you opt for a pay-as-you-go phone, you can still get the deal, but only for 30 days. More details can be found here.