To expand on Client62’s answer above, it is quite possible that a neighbour of yours, connected to the same street cabinet, had an issue. When the tech turned up to ‘fix’ it, what they did was to identify it as a low power issue and the obvious fix is to to move their connection to a lower attenuated tap in the cabinet.
Fine, except what happens if there isn't a free port in the cabinet? The temptation is to simply move someone else’s connection and this frees up a socket for them. The job that have been sent to fix is recorded as successfully done, they tick off another successful call/job. Of course in doing so they may well have caused issues for another customer, but the important thing here is that ‘this is not their problem’!
That’s actually your problem and a problem for the next tech to come out to you - who seems to have fitted a powered amp to mitigate against the low power values; note that this isn’t necessarily always a good option as it also amplifies ‘noise/interference’, but it seems in your case it’s working so let’s not knock it!
Of course, all, of the above is pure speculation - not unreasonable though!
