Outsurance living up to it's poor reviews! Third party abuse

My husband was involved in a fender bender with an outsurance client. After the client filed for a third party claim for us, we have just been informed that we will not be compensated at all for the damage due to some previous paint damage on the bumper. The outsurance client driving a much larger vehicle reversed straight into my husband who is driving an i10... The number has been cracked and torn by her vehicle but now we have been refuted for the claim based on prior paint damage. So who exactly is liable for the damage your client has done?!??!?