If you write to them try this first -
http://www.pureesoiree.be/forum/topic.do?id=70 605
It's been on here before i believe, but is excellent!
Last year when i changed my name due to marraige i rang and asked them to update my details. They still havent - as i refuse to send in my requested certificate for them to lose, so having received my notification of their name change i wrote and informed them that i would require legal documentation to that effect and would not be paying any bills until this was actioned. I explained that this should not be a problem as it is one of THEIR policies so they should understand this. If they were not willing then they should also understand my reluctance to forward said document.
They wrote back informing me that i should send in a COPY of my certificate and if i require legal documentation re their name change, i should contact a solicitor! My latest reply stated that as a Marraige, Birth or Death certificate is a Copyrighted document, this will not be possible!! The saga continues! Good luck m8 - you'll need it!