"Great, but appointments need to be kept."

I have been waiting to get my braces taken off for a long time, and got a letter saying they were coming off in early June, so I was very happy. A week later I then got a letter saying my appointment had been changed to early July, and the next day, received a letter to tell me my appointment is now in August. I called the hospital explaining that I need them taken out earlier desperately as it would affect my exams and the member of staff on the phone was extremely polite and managed to return my appointment, but now to late June, so I was still a little annoyed but satisfied. Today I got another letter telling me that my appointment has been moved again to late July. This is terrible, my appointment to get my braces taken off has been changed 4 times and every time the reason was, 'changes had to be made in the clinic'. I wish my appointment could have stayed on the original date of early June.