We noticed on our post paid bill that there were a huge number of charges to numbers in the UK. We called BTL and a rather unhelpful rep tried to tell us that we were sending the messages "unconsciously" via iMessage on our data plan (even though most were sent at night when the phone was connected to WiFi). BTL admitted that they have been aware of the problem for months. They haven't told anyone though and they continue to bill post paid users for the texts unless you bring it to their attention. Not everyone receives a printed statement so they may be unaware of the charges. BTL says that pre-paid phones aren't being charged even though a check on a pre-paid phone's records showed SMS messages to the same numbers. Check your post paid bills and if you don't get a copy get one back to at least October when the problem started. Take your bills to BTL and demand a refund for the charges. Here is a link describing the problem, it is worldwide. https://discussions.apple.com/thread/6518670?start=0&tstart=0
It should be noted that the rep said they haven't said anything as most people don't have iPhones except tourists that come and don't go home. You can read into it what they meant by that.