poor service

unable to renew sickly mom's car disk, Randburg post office refuses to renew a vehicle disc, saying I need a letter from the car owner who is currently undergoing dialysis and needs to go to hospital 3 time a week, The car is needed for transporting her and The post office will be liable for any fines received after this day, because the disc has always been renewed without letters. I am the daughter and had her ID as well as mine.