Car service incomplete

I sent through my car for service at Peugeot Hatfield on 13 October 2015. The dealership called that the car was ready for collection at 2pm. My mom went to pick it up and she was told that certain parts needed to be replaced but were not in stock, needed to be ordered BUT still gave her the car. Wednesday 21 October 2015, a lady called to do a customer service survey, I explained that the are car parts that were supposed be replaced but was not done and believe were on order. She said she would follow up and get back to me and never did.