Poor service

On 31.08.18 I ordered a pizza and paid online from debonairs Banbury crossing, it was confirmed by the store at 19:42. The pizza was only delivered at 20:56, more than hour since ordering and it was cold. All the driver could was "sorry we are busy". I then tried to call the store was kept on hold for more than 15min with a voice citing high call volume, I finally gave up and dropped the phone. On 01.09.18 I proceeded to call the store and spoke to the manager, Beatrix, who then apologised but wat came out of that call shocked me. Beatrix said she would give me discount on my next order. Excuse me but I thought debonairs promise is that if the pizza is cold or the dot is black the pizza is free. Is this just part of marketing to **** customers? Why ****es off the most is that this is not the first time i get cold pizza from this store, I'm disgusted. The call got cut off and i called back but was told Beatrix is not available hardly 2min later. I left a message for her to call me and it has been 2hrs of no action. What measures doe one need to take to get good service and my money back?