poor service

My car was booked into Renew-it after an accident nearly a month ago ,within the first week my insurance assessed the car and renew was given the go ahead despite a huge discrepancy between them and my insurance with the quote .About a week ago I received an email to inform me that my insurance had given the go ahead again ,this week I have been informed that the parts are being ordered so what has been happening for the past 3 week? When I phone to find out the person is unavailable or when I talk to a guy called Fernandez and a women called Elize Im told the parts are for a second job on the car ,the second job is a small scratch and dent which I agreed to them fixing at own expense and does not require parts.They tell you that they will come back to you when they have found out more ,however they do not come back and I find myself making endless phone calls. The worst of it is thisafternoon I get a message on their Web page stating that their is a a delay in repairs ,so despite my endless phone calls and clearly fustrated behaviour no one could pick up the phone to inform me about this and communicate where to going forward.How can I trust them to fix my car?