I dont usually post on forums Im usually a reader but I felt I had to share my experience. Yesterday I was playing in the garden with my GD and I received a text message. It was from my mobile provider so I glanced at it and then returned to my GD. Unfortunately I didn't read the message fully and it informed me that I had used up all my monthly data allowance in my contract and would now be charged.
later on my own I discovered that although I hadn't actually been using my phone in the garden its still downloads messages and updates, so I now have charges over my monthly contract. Luckily I also have a 'buffer' which restricts the amount of charges. Ive also changed the settings on my phone to stop this happening again.