EllieandCraig:
Why don't you phone the Otelo helpline to see if this is something that you can complain about. If it is then you could submit a formal complaint to Orange using their complaints procedure and if they do not reduce your bill, you could then submit to Otelo.
http://www.otelo.org.uk/pages/13contactus.php
I have read numerous cases in the press, where phone companies have agreed to reduce bills in very similar circumstances. This was on the basis that the charges were not seen to be fair for the service that was provided.
Huckster