I think possibly you can talk to BT Openreach directly if you want to get the cable moved? Because iirc I saw that there is a contact for a department that handles such things for people doing building work, so this might be basically the same thing and they could at least put you on to the right department. Otherwise it will mean talking to your 'phone service provider', that is, who ever it is that you pay your line rental to. If Openreach are jobsworths then they might say that to you. Toss a coin and maybe try one or the other first. The Openreach website might be the place to go for department contact info.