No, you do not pay grandma. You will receive a letter directly from the insurance company that paid the claim. It is a subrogation letter. They will be asking you to reimburse them for the damage that they paid, due to your son's negligence. However, you will be paying more than $550.93. You will also pay the not at fault party's deductible, which usually ranges from $250 to $1000. All of that information will be on the subrogation letter. Good luck. Tell grandma to bite rocks.