I had a problem 3 years ago where the database was wrong (wrong PCP identity), and it needed my ISP (Plusnet) to fight hard to get it fixed.
At that time, neither the BT nor Openreach CEO was willing to do anything to sort the problem out.
Here, TalkTalk ought to be the ones sorting you out. Given that they won't act, you've taken the right step to contact the Openreach CEO - a route that seems to work better these days.