It’s nothing really to do with BT, if you report a problem to your provider (BT) and the ‘fault’ is accepted as something ‘real’ that needs attention, then it’s Openreach as the supplier to BT , that are responsible for checking ( they provide the service , and that should meet a documented standard ) and investigate if the service is not up-to scratch.
OR with the fault information provided by the consumer as well as line test results, decide where the fault is likely to be , they don’t get ‘instructions’ from communication providers ( like BT , Sky or whoever ) where to look or not look, apart from anything checking in a PCP ( the usually green street cabinet ) is an easy thing to do, it’s not like a faulty underground cable that cannot be seen, or a problem that is present when it rains but not present when it’s dry, so it’s pot luck if the fault is present when the technician turns up.
If you have a fault history that shows you repeatedly reported the same issue , is obviously an indication that a problem existed and wasn’t satisfactorily resolved you may have a case , but AFAIK, when a fault is raised , you are contacted when the fault is ‘cleared’ and asked if you agree the issue is now resolved and if it isn’t , you get the option to state the fault isn’t fixed, if your fault reports have large time gaps between then , and you accepted at the time the fault was fixed , it may be difficult to argue a case that your service was disrupted ( much ) , it may even be the case that they can check your individual line connection stats, and know how many times and for how long your connection dropped.
