Terrible service

I logged a windscreen claim with my insurance company and they told me that Grandmark Autoboys is their preferred service provider and that they will respond within 4 hours. I got an sms 12 hours later giving me an appointment date. To question as to whether this date and time suits me. I phoned them to reschedule as I had taken a day’s leave for that day. They told me that it is the earliest they can help me but that they will be able to come very early in the morning so that I can still leave at a reasonable time for my long weekend. On the morning of said day, they phoned to say that they are coming at 11:00. I reminded them that they promised to come at 08:00. Again said that unfortunately 11:00 is the earliest time. They only arrived at 13:00!! After 45min of working on my windscreen, they realized that they have the wrong size windscreen. So after wasting my previous leave day, I still didn’t have a new windscreen! Again I got an sms with a rescheduled appointment. I arranged to be off work to go in to their workshop. After 30min of them working on the windscreen, they came back to say that it is the wrong size yet again! Four days later they phoned to say that they cannot find the correct size glass and will need to order from Renault. It would mean that I have to pay for excess. I said it is fine and they must please order the glass. I got an sms telling me that I need to come to their workshop today. I phoned yesterday to ask if they can come to my work as I cannot take more time of work. She promised to phone me back with an answer. I never got a call back. I phoned again this morning to ask if they can please come to my work. Now they tell me that they are still waiting for my insurance company to approve the new windscreen claim and then it will take 3-5 days to order. That will make it more than a MONTH since I submitted my claim. (I am selling my car and needs to deliver it with a windscreen) So this people are preventing me from getting my new car with this delays. I phoned my insurance company and they said the claim had been approved a long time ago so Grandmark is lying about waiting for approval. I am just so annoyed!