They may have got name, email address and address from a number of potential leaked sources as there is a mass of data available on the dark net.
BT service over 1/3rd of all UK customers so even by chance they would have a 1 in 3 probability that whoever they ring would be with BT - it doesn't have to be something BT have leaked.
Yeah we get a few on our landline, if its an actual person we just say they are not BT and if they are to call the correct contact number and to then hang up.
But most of the time the fake BT calls are just automated voice wanting you to press a number on the keypad, we just ignore those calls and just hang up on them.
Have you ever had the calls from companies saying they are ringing in response to you reporting a car accident? A relatively small number of people would say "yes" and yet it is presumably a large enough percentage that they can make money from scamming those that do.
I have had this type of call twice, both times they first ask how are you and then go on stating why they are phoning, I then respond in a calm voice with "How are they, and if they are ok" which they respond yes, I then say to them "this is a scam phone call and you know it and if you keep calling me you won't be ok" and then wait for about 10 seconds, to hear them hang up.
That was 3 years ago and no more of those calls.
I know I shouldn't say that, but what are they going to do.