3 months to fix a car

I had to wait for atleast 2 weeks for my car to be booked in, upon booking my car in I was informed that parts will be order and that the process takes between 3 to 14 days depending on avalability of parts. They only managed to order and get the parts 4 weeks later. I was further informed that the repair process takes 3 to 4 weeks. 5 weeks later I am still waiting and my car is on stage 4 of 9 of their repair process. NB, it is not the engine that needs changing, they only had to change the doors and the back part. I will never refer anyone to this panel better. The Manager is so defencive and never apologises when asked about the delay.