Worst experience ever!

Prior to the lock down due to Covid-19, we had booked a taxi with Just Car hire for June 2020. I have been trying to call them from the beginning of May to request an extension or refund, I have called more than 20 times and emailed more than 15 times and I have not received a response to date. I am actually disgusted at the level of service or lack thereof. I am actually not sure what to do.