Greyhound won't refund cancelled trip from Kimberly to Joburg.

Had a trip booked for Aug 2023. Decided to fly so called Greyhound to cancel. Was sent an email with forms to fill in. Did that and promptly sent them back. Have not heard a thing since despite numerous emails chasing their refund department. Every time that we call we are put through to the refunds department which rings and then hear a message that voice mail has been disconnected. We have tried to call them 24 times!