Have had this intermittent problem for over 2 years now. I lose dial tone and am unable to receive calls for several hours. Have checked all equipment by unplugging and have purchased a corded phone which also does not work. This problem persists even in the test socket.
BT have been informed 3 or 4 times now and have sent out an engineer who came when the phone was working and obviously found nothing wrong for which I was billed £130.
i had the same problem, but instead of getting bt out £130+ vat i found a independant telephone engineer who had worked for bt so he knew what he was doing. he checked out my home wiring and said all was ok and the fault was in bt's network. cost me £40 but took the risk of having to pay £130 .