Don't even dream of taking a mobile phone into afghanistan, it will be more costly than you could imagine. Mobile phones are not allowed for very good reason, not just security but your own welfare and well being too.
Have a think about it and if you still want to take one.... have a word with yourself! If that doesn't work go ask your chain of command how much calls cost from Kandahar!
I went to Iraq and some WAP company sent one of those spam texts offering lots of free porn for Â£2.50 (kind of takes away the idea of it being free if you pay for it!)
I found out the hard way that with it being Iraq not the UK, they don't need a reply text, so they kept sending me these texts. Found out that it was costing me about Â£450 a month!
When I phoned up Vodafone, I found out that this has happened to quite a few soldiers. The problem is that this isn't illegal in Iraq and the company is based abroad, so as long as they follow their laws and Iraqs laws, then there is nothing that can be done about it!