Hi,
I am an ex- Bt engineer, and, if you don't know, if the fault was in your proprty you will be billed for £130 plus £90 per hour. May i suggest that you write down the date and time of visit, how long they were there, and what they did. Also, did BT tell you to remove the small front plate on your master socket and prove if the fault was inside or outside? if they didn't, you can get away with not paying the charge. Also, were they BT, or contractors?? BT have no staff, and are recruiting as fast as they can, and the chances of more than one BT engineer turning up is virtually impossible.