In fivecandles' example yes, the patient could have phoned with the new address, but it's probably not the first thing on the mind of a young schizophrenic who may well be attempting to avoid any sort of follow up.
When I worked as a medical secretary, if someone had telephoned me to say they'd received a letter intended for one of our patients, the first thing I'd do is look out the patient's notes and phone them to find out their new address. Then I'd get all the records changed, both manual and on databases. If I had no joy with the patient themselves I'd be ringing the GP. There is no excuse IMO for more letters to be sent to the same, wrong address, especially not now we have computerised systems, or even in the days of only paper records.
IME there are some workers in the NHS who don't think things through and don't appear to care about the implications of their actions or what they don't bother doing.
My Trust does training for admin staff, but for many, many years prior to that it was unknown IME. I've seen many a post filled with people who just don't know what they are doing. There is no induction, no training and the managers (IME) haven't had a clue themselves about the role. It's always been left to colleagues who are already stretched, and who have probably been struggling to cover the vacant post so are overloaded with work and stressed, to find time to train the new person. And in doing that their own job gets behind, appointments don't get made, letters to GPs don't get typed, the phone calls start coming in because the letters are needed .... and so on.
But I maintain that no matter how stressful the job is, no matter how many rude patients you speak to there is no excuse for being rude to the next person who happens to ring. And I have spoken to enough GP receptionists and medical secretaries in my time to know that it happens way too often for it to be a one-off. There are some lovely, friendly helpful staff out there, but those that aren't are definitely there and IMO there is no excuse for it. You just don't speak to patients and other staff like some of them do.
And it's interesting that the change in their attitude when they address the GP was mentioned. That is my experience too. If I have phoned and they've missed the "secretary" part of my announcement "hello, it's Dr Surfer's secretary here" their attitude has been vastly improved just because they thought they were speaking to the doctor. I had it just last week when I was trying to ascertain some information about one of our patients - I spoke to a very unhelpful GP receptionist until the point at which I told her I was the unit's Bed Manager and I couldn't believe the change in attitude. As if it mattered who was ringing. But just because she was speaking to a manager her attitude changed.