"fed up of chasing!"

I was told in March that I needed surgery. The staff at this point were fantastic however it has gone down hill since. I was told it was an 18 week wait. In April i contacted Patient services to let them know my holiday dates and to enquire as to an approximate date for surgery as I need to let my boss know. i work in a school and therefore my class will need cover. I was told the wait was now 15 weeks and to call back in mid May and they should have a date for me. This week I emailed them as agreed, especially as my boss has now sorted the classes out for September and needs to know how long I will be away from school for so that she can inform parents and for my cover to meet my class, to be told that the wait is now 20+ weeks! what on earth is going on why am I the one that has to do the chasing?? Why does the waiting period keep changing? All I want is a provisional date so that I can give the information to my boss, however this seems too hard for people to do. Seriously wish I had been sent to a different hospital now as I am sick of all the chasing