"Still waiting..."

Called for an appointment 17/04 - given an earliest appointment of 29/04 - despite explaining to reception that this was a follow up appointment for a treatment that has not worked. Almost 2 weeks later, I arrive 10 mins before the appointment and self-check in which confirms my appointment details. I'm then left waiting for 50 minutes in the quiet surgery (no more than 3 people sat waiting at one time) before I approach the reception desk to find out what's happened. My appointment has been cancelled and a text has been sent to an old mobile number. With a consoling "this is why we ask you to keep numbers updated" I'm then offered an appointment for the 13th of May! Almost a month after my initial call. As this wasn't a new appointment, but one that the surgery has cancelled, I was quite shocked with this and pointed out that I have already waited almost two weeks for my appointment. Final offer - 10/05.