"Disappointed waiting for a follow up app"

My 17 month old son was referred when he was 6mths and it took nearly 5 months for an appointment. The service while at the appointment was great and I felt comfortable leaving with the receptionist saying they will send a follow up appointment through in the post in in the next 3-6 months. However it is now 7months on and still no appointment. I rang 3 weeks ago and was told they would ring me back as the didn't have the right code. Not sure what that has to with an appointment but she promised and said I won't forget. However she did and I was not called end back. I rang again the next day but would only be put through to the appointment line where the lady said there was no record of me ringing but also they had no appointments so she would put me on the spreadsheet that would be sent to the eye clinic direct and an appointment would be set and sent in the post. I did express I was not happy with this as I feel we are being messed about and this is such an important issue. So nearly 4 weeks on and guess what yep no appointment. I have rang for 2 days solid now and can not get through. I am not sure what we are supposed to do this is reciculous and my son should not have had to wait this long.