In that same email, it says:
"As of 1st January 2013, the following changes will be made to our contact details:
• For queries relating to an existing booking that you have, contact British Airways."
Granted it's not 2013 yet, but at the moment they're totally screwing us over by not allowing us to contact them via the DC phone number or to help us via the BA number. I have my doubts that they will be able to help after January 1 either, being the BA agent I spoke to made no mention of requesting me to call back in a few days after they're supposedly going to be handling DC bookings. You'd think if they were, they would have already been informed and trained in the matter.
For all the goodwill that BA may have generated in their takeover of BMI and transferring BMI miles to Avios, now they ended up doing more damage to their reputation/credibility as far as I'm concerned, unless they get someone to fix this mess.