Old mutual insurance lies

In 2018 I had a car accident, the driver behind me failed to stop at a yield stop and rammed into my back bumper. I captured all his details as per instructions of my broker. I then had to pay R 5000 excess and Old mutual promised to recover from the bad driver. Upon making inquiries June this year to retrieve my 5k I was told he would be paying R500 a month and I accepted the offer. In November 05 I received an email from old Mutual stating that they can no longer locate the person and they are closing the case . They are now saying I should take the person to small claims court. What is the point of making promises you can’t keep.