[danielf]

Originally Posted by Paul H

Yep, so that'll be Premium rate and mobile numbers as they're not included in the plan, so you'll be dialling them outside the plan.
This is what the letter is trying to say, it can't be any clearer than "there is a £5 charge if you don't pay by direct debit"

I don't think that is what they are trying to say, but I agree it could be interpreted that way. But, as others have said, I think you will have a very hard time arguing the case with CS.