Similar but simpler problem to jh2007:
Moved into new property which has three phone sockets. Presume all connected to same line (no reason to think otherwise). No idea how you can tell a master socket from a non master socket. Only one is active. Rang BT and told that I have to hire an electrician to come and turn them on. Letting agent / Landlord say that they won't do that as it's BT who should have activated all the sockets when they turned the line back on. Rock { me } hardplace.
Is it really true what I was told by customer services that there is no option other than to hire an electrician myself for close to a hundred quid for they day? Or pay £90 for a BT engineer for the day? Seems so unlike the usually excellent customer service I have come to expect from BT.
There are some pictures of sockets here. You should be able to identify the master. Anything after that point is your responsibility.
Unless you asked bt for them to be activated and paid for this to happen then you need to get them sorted yourself as BT dont maintain extension sockets unless fitted by BT and then only guaranteed for 12months.
Openreach only maintain up to the master socket. When your service was activated any previous working socket would spring into life, there is no machine or system that will pick and choose what sockets start to work when a line is activated so best guess is they are not working now because they didn't work in the first place.
And yes what BT customer service was saying is correct, as the extension sockets are NOT owned/maintained by BT or Openreach then you can get a third party in to fix or wire them up. Or you could pay for an Openreach engineer to come do it for you, you would need to place the order via BT but it will set you back a fair bit because they charge £130 for the call out and £75 per extension to be connected.