Not willing to fix my vehicle's mirror

I tried to claim from my insurance because somebody drove into me and it damaged my right hand side mirror. Mi-way refused to fix it because they had to claim from the other person's insurance and was not willing to do so. I also don't understand why the excess is the amount they gave me, it was only the mirror that was damaged. Then why even give me an excess amount if they are not even going to fix the mirror? I am currently looking for other insurance because this is poor service and just unacceptable. Why do I pay for my insurance every month if this is the service I am going to receive?