Poor feedback on a complaint

So I was involved in an accident where my car was bumped on the side and my insurer king price got the damage fixed in about a months time which was great. However on receiving my car I noticed that I had a about half a tank or so of fuel missing from the car so I asked if the panel beater if they had to test drive the car a lot and to my surprise they said no they got the car with the fuel where it is. I then contacted King price wot find out what happened and 3 weeks later I'm still being told the same story of, we are looking into it an email has been send and we have escalated the matter how ever as I'm writing this review we are heading into the 3rd week and the has been no progress on my complain, as a customer that is grateful to have their claim honored I'm also frustrated in the lack of action on this issue because I did not choose any of the service providers involved in handling the vehicle and when the is an incident it would be nice if it is responded to with the correct action required instead of waiting for a service providers email for 2 weeks now heading towards the 3rd week after I have followed up weekly to find out what happened.