You have been charged 36p per minute which appears to be the rate for service numbers or the cheapest personal numbers.
You should be able to get a refund if you ring 789 and explain. It's probably a temporary glitch, they appear to be doing some updates tonight. I had to get the call costs from Google's cache, as parts of the site are down.
Thanks for the reply Goff. Unfortunately I don't share your confidence in the CS staff. Based on past experience, at best I will be caught in a spiral of calling to plead for each previous 789 call charge to be refunded. Can a forum staff member confirm that, if an error was made, CS will refund both original overcharge and the cost of the call to claim this back?