Terrible customer service

I would give this zero stars if possible!

I contacted Safestyle in January to report a faulty window in my soon to be new borns room. I was given a date 6 weeks later, to which I accepted and as I work shifts I booked this day as annual leave to accommodate. I got a phone call less than a week before the appointment to be told that due to sickness they would not be attending the appointment and gave me an appointment the following week which I told them was unsuitable. Even though I stated it was unsuitable it was booked anyway!
I have been trying to contact Safestyle on several occasions getting the same response back, terrible customer service. They refused to give me an option of dates to work around and I refused to book another annual leave day. When I stated I was going to go to an external supplier that would accommodate me on a weekend of evening I was told that this would invalidate my warranty. But I am unsure how I can get my window fixed in time for my new arrival now! I have made several complaints which have not been taken seriously and have not been contacted regarding this. I would never use this company again.