...just tried to check my available data on my O2 PAYG mobile dongle. Normally when I do this the number comes up automatically. This time it didn't, and asked me to enter it. I hadn't a clue, and did not know where I had kept the card with the number. A message appeared, "Don't know your number? Ring *** and we'll get it for you. Rang the number and got through to the nice robotic lady with the posh voice. Her first instruction, after the welcome, was, "In order to help you, please enter the number you are phoning about."
Err...
Fortunately a light bulb went on and I realised where I might have kept the card, so no harm done, but really!
She wasn't simply asking for your mobile number then ?
Could be disconnected thinking. There will have been a service that required this dongle number. Then at some other time someone thought, "I've an idea, if they can't recall their number tell them to dial the help number". Not working out the consequence. It can easily happen when you have different teams doing different things.