If you have a bill due I would advise you to check it carefully and especially if you have an evenings and weekends free phone package.
I checked mine yesterday and found I had been charged for evening calls on Fri 21 Feb, Mon 24 Feb and Tues 25 Feb. According to the chap I spoke to (possibly in India) BT had a computer glitch at that time and he has refunded the costs to my account.
I find it sad, though perhaps inevitable in this day and age, that although BT were aware of this situation they chose to let customers find out rather than to have advised them! I shall be taking up this with BT in writing.