Bad service delivery

This company delivers medicine to my 85 year old mother in Walkerville. She renewed her prescription with her Doctor who sent it to them. They call her everyday and harass her. They tell her that she has to pay in R34 or she won't get her medicine. She cannot walk or drive. When I call, the whole place is busy on their phones. I leave messages every hour and no-one phones back. My mother is already on anxiety pills and this is making her condition worse. Why can't anyone call back?