Discount Car and Truck Rentals

We ordered a rental from discount car and truck near the Sydney nova scotia airport through the online booking system. We were given a confirmation code. When we arrived they told me "oh sorry, we didnt have your phone number, we overbooked and we don't have a car for you". We were abandoned at the airport, I asked the other car companies of they had vehicles and they did not. They also told me I was the 6th person that day that discount had done this to! When I called discounts national number to lodge a comkplaint they couldn't do anything to help me, and said a manager would call me back in 2 to 3 business days. Then asked if the number I had on file was correct, so they did have my phone number! And chose not to call me to tell me there was no car!! This is the worst customer service I've ever seen. The manager has still not called me. We had to take a $70 cab ride to get to Louisbourg where there are no cab companies or buses and no way for us to get around thanks to discount.