With iPhones, in order to use either iMessage or Facetime, your phone will send 2 silent TXT messages in the background to the UK to +447786205094. This is done in order to activate both Facetime and iMessage applications with the Apple server which is based in the UK.
If either service gets switched off, or disconnected from the server, or if you take the SIM card out of your phone for example, your iPhone would automatically send this TXT to activate it. Each text costs $0.31 to activate.
This would usually happen only once when you first start using both applications, yet if you're turning either app off for example, have no data connection for extended periods of time, then your mobile will send those international txts again to reactivate it.
Please do the following to prevent these text message
To disable iMessage: Go to Settings> Messages> Tap the iMessage switch to the Off position.
To disable Facetime: Go to Settings> FaceTime> Tap the Facetime switch to the Off position