Delays, Delays, Dalays, and more bad service

I took the car to this so called services bla bla bla, i took my car there on the 25th of May, until today when i call them they keep saying that it will be ready the next day, it's very disappointing to get this kind of service as we are paying for it, they even went as far as telling me that there are so many cars that they have to deal with, so i must wait until my car is done, but how do keep someone's car for such a long time?