Well not everyone sends a text message every minute of every day Kev, but yes that is a problem and if they really didn't inform you then you should be able to get the money back really.

...and I'm only guessing that after this you are rather put off seeking employment with them

I rarely use my phone, I just have a pay as you go phone and I hardly phone anyone, and just usually send silly text messages, maybe 20-30 a week when in Uni. Over the summer though I probably won't use it too much.