Can't buy Crowns via SMS?

I'm trying to get Crowns to upgrade to VIP, however, every time I try, I get the following message; "Hi! Due to legal requirements in your local area, we are unable to offer payment services at this time. Please try again in a few hours." It's not particularly helpful, and (being in the UK), I know that the "local area" part is a load of rubbish, especially as I've bought similar things via SMS in the past.

Any shed light on the matter would be greatly appreciated.