Refund on bus tickets

I have an issue. I booked 6 bus tickets with Hope Diamond bus which was supposed to pick us up from Durban Station to Johannesburg Parkstation. Departure time 11:00. When we got to the bus station we were told that the bus is not available it will be available at 10pm. When I tired calling they did not answer calls and I sent them an email. They responded I requested a refund as I had to make other alternative arrangements and book another bus with intercity which was an inconvenience for us. They responded and requested evidence that I made other arrangements now they not responding.