"Cancellation of my outpatient appointment"

I went and had my field tests done and knew that I had a follow up apt for next Friday at 9.20. Today, Friday 26 Sept I receive a letter altering my apt - they say - Unfortunately we are not able to offer you an alternative apt at this time. I find this totally unacceptable. I have borderline glaucoma and it is important that I have eye checks every 6 months. Before I moved into this area I never had trouble at my previous area's eye unit. It is not acceptable not to give me an apt date! Furthermore, when I was up having my field tests done, I was not told by the nurse that I could go home so we waited an hour and a half and it was only when I enquired when I was going in that I discovered that I need not have waited. It would surely be obvious and courtesy to say to patients we will see you at your follow up on whatever date. I was concerned about floaters - another very nice and helpful nurse had a word with the dr and then conveyed a message back to me - not very re-assuring to me - the patient! Additionally, I have been on the phone and held on and on for over 15 mins and not moved up the queue at all - again far from impressed!