"Short notice appt. change led to discharge"

Extremely frustrated with this department. I had a four month follow up appointment booked. I received a letter a number of weeks which brought the appointment forward. This was for today. I've just found a letter which brought my appointment forward again, but within one weeks notice. I missed this appointment as I was away when the letter was sent and the appointment was re-booked. On phoning the department, I have been told that I have been discharged due to failing to attend and will have to return to my GP to contact the doctor and ask them to see me again. Very upset by this and so frustrated that I have to start the process again, thanks to their failure to notify me in time or check I had received the rescheduled booking. I have Aspergers Syndrome, so getting the original referral was not easy for me and the unfair discharge affects me more than just the inconvenience.