Bad repair process and follow up

Repair management process does not take into consideration the clients needs. How do you send such respond to the client instead of ensuring that the repairer gets the job done on time and not to inconvenience the client. They have an SLA with the repairer not me. "As per on our system your car hire is due back 28/07/2023. Unfortunately, we are not in the position to extend the car hire as we do not compensate for parts delays and / or parts on back order – however you can extend the car hire for your own account"