The number to call is 17070. You will be given a list of options, I think a QLT is option number two.
There should be no noise, no hum, no buzzing, no clicks, no overhearing of "Glenda Gossip" in full-flow . . . you should just be aware that the circuit is electrically live.
If you decide that there is a fault, it should be reported to the entity that supplies your telephony service. You should report it as an audibly noisy telephony circuit and do not make any mention of the broadband service which also shares the circuit.