Yeh has happened because someone rang & i didnt get there in time so bt 1571 took the message & that leaves a broken dial tone, & another is usually cos me bro or someone has accidently rung my no in their pocket & not realised if they dont end the call then it does leave your phone unable to be used incoming or outgoing till they end it, tho that tends to have no tone but muffling noises & having to shout down phone for em to realise or hope their battery or credit conks out
