Bad service i got

My claim number is : ********** 73 and my policy number : ********** 62, I have been contacted by the Repairer on 06 December (L & M Autobody repairer which was assigned by my insurance to fix my car) and I was told that they have ordered a rear bumper which they will received it in three(3)weeks from the day they have ordered it , meaning that my car will not be fixed anytime soon and they have closed on the 14 december and I refuse to go take my car which was not complely fixed as advised by the repairer that they can put the old bumber for now so I can use my car untill the bumber is delivered. The courtesy car from AVIS is expiring on the 22nd of December and after that I won’t be having a car , and I was told that before the repairer closes my car would be fixed and the insurance arrange a 30 days courtesy car for to allow the repairer to fix the car . When I ask the repairer as to why the delay they said the insurance have decline a quote for the piracy parts that the repairer wanted to buy and told them that they must buy the original parts instead of piracy ones and the insurance didn’t authorized the piracy ones and these is not my fault at all. I was expecting my car to be fixed by now. When commucated these with my insurance asking them to extend that 30 days untill the repairer fixed my car and the response from insurance was that "old mutual cannot be held liable for any parts that are in back order and they are unable to assist me with the extention for the courtesy car" so meaning that I won't be having a car to drive from 22 December untill my car which is at the repairer building got fixed when they re_open in January 2019 please assist, becourse the insurance hide behind their policy and the reason I got a courtesy car was to allow the repairer time to fix the car, which the repairer fail to do so. Am very frustrated and angry by service I got from my insurance. I sent the complain to my insurance on the 13th December and they responded to say they have received my email and the matter was ascalated to the relavent person to assist and I only got feedback today from them when I called to make follow-up and if I did not call them they would have not yet responded and I feel like old matual have failed me and they should have communited with me that they did not authorize the piracy parts with the repairer and come up with a solution to these matter and with the experience they have working with repairers and festive season majority of the repairers closes on the second week of December and kwowing that it's gonna take time , they should put something in place to resolve these issue rather than to play a blame game with the repairer because am paying my premium every month to my insurance for me to get a service I deserve and they don't want to be accountable